Optical disk, optical disk barcode forming method, optical disk reproduction apparatus, a marking forming apparatus, a method of forming a laser marking on an optical disk, and a method of manufacturing an optical disk

ABSTRACT

Disclosed is an optical disk barcode forming method wherein, as information to be barcoded, position information for piracy prevention, which is a form of ID, is coded as a barcode and is recorded by laser trimming on a reflective film in a PCA area of an optical disk. When playing back the thus manufactured optical disk on a reproduction apparatus, the barcode data can be played back using the same optical pickup.

This application is a division of U.S. patent application Ser. No.08/649,411, filed May 16, 1996.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an optical disk, an optical diskbarcode forming method, an optical disk reproduction apparatus, amarking forming apparatus, a method of forming a laser marking or anoptical disk, and a method of manufacturing an optical disk.

2. Related Art of the Invention

In the manufacturing process of optical disks, it has been commonlypracticed to record a serial number, lot number, etc. on each opticaldisk in the form of a barcode.

Since such information cannot be written to a pit information area ofthe optical disk, it has been practiced to write the barcodedinformation to a non-information area, or unused space, on the opticaldisk.

When reproducing (playing back) such an optical disk, the pitinformation is read by an optical pickup; to read the barcodedinformation such as a serial number, etc. recorded in thenon-information area, however, a separate reading device has been used.

In the above prior art optical disk, since information carrying a serialnumber and the like is not recorded in a pit area but recorded in anon-information area, as described above, a separate reading device hashad to be provided in addition to the usual optical pickup, theresulting problem being increased complexity of the playback apparatusconstruction.

SUMMARY OF THE INVENTION

In view of the above problem with the prior art, it is an object of thepresent invention to provide an optical disk wherein data such as a diskID number, etc. is converted into a barcode and recorded in a pit areain overwriting fashion, thereby permitting the use of a single opticalpickup to read both the bit data and barcode data. It is another objectof the invention to provide a barcode forming method, etc. for such anoptical disk.

One aspect of the invenion is an optical disk on which data is recordedwith CLV, wherein, in a prescribed region of a pre-pit signal area onsaid disk, all or part of a barcode is written in overwriting fashion byselectively removing a reflective film in said prescribed region.

Another aspect of the invention is an optical disk according to thefirst invention, wherein a control data area is provided for holdingtherein physical feature information concerning said optical disk, andan identifier for indicating the presence or absence of said barcode isrecorded in said control data area.

Still another aspect of the invention is an optical disk according tothe second invention, wherein a guard-band area where no data isrecorded is provided between said control data area and said prescribedregion of said pre-pit signal area.

Yet another aspect of the invention is an optical disk according to thefirst invention, wherein said barcode is formed in such a manner thattwo or more barcode signals cannot occur within one prescribed tireslot.

Still yet another aspect of the invention is an optical disk accordingto the first invention, wherein said barcode contains data at leastincluding ID information uniquely given to said optical disk.

A further aspect of the invention is an optical disk according to the5th invention, wherein said barcode contains data including, in additionto said ID information, a public key of a public key encryption functioncorresponding to said ID information, said public key is used to encryptprescribed data, and the encrypted prescribed data is transmitted to anexternal party in order to obtain from said external party a passwordrequired to reproduce said optical disk.

A still further aspect of the invention is an optical disk according tothe 5th invention, wherein said ID information is encrypted or applied adigital signature to.

A yet further aspect of the invention is an optical disk according tothe 7th invention, wherein a secret key of a public key encryptionfunction is used when applying encryption or a digital signature to saidID information.

A still yet further aspect of the invention is an optical disk accordingto any one of inventions from first to 8th, wherein said optical disk isconstructed from two disk-substrates laminated together.

One aspect of the invention is an optical disk barcode forming methodwherein pulsed laser light from a light source is made into arectangular beam pattern by using a rectangular mask and saidrectangular beam pattern is focused on a reflective film in a pre-pitsignal region in a prescribed radius portion of an optical disk on whichdata is recorded, and at the same time, said optical disk is rotated,thereby forming a plurality of rectangular reflective-film-removedregions as a barcode in the same radius portion on said reflective film.

Another aspect of the invention is an optical disk barcode formingmethod according to the 10th invention, wherein said optical diskincludes a control data area for holding therein physical featureinformation concerning said optical disk, and an identifier forindicating the presence or absence of said barcode is recorded in saidcontrol data area.

Still another aspect of the invention is an optical disk barcode formingmethod according to the 11th invention, wherein said barcode is formedin such a manner that two or more barcode signals cannot occur withinone prescribed time slot.

Yet another aspect of the invention is an optical disk barcode formingmethod according to any one of inventions from 10th to 12th, whereinsaid optical disk is constructed from two disk-substrates laminatedtogether.

Still yet another aspect of the invention is an optical diskreproduction apparatus wherein recorded contents of a recording area,recorded by forming pits on an optical disk, are reproduced by using arotational phase control for a motor, while recorded contents of adifferent recording area other than said recording area, recorded byselectively forming low-reflectivity portions on a reflective film insaid different recording area, are reproduced by using rotational speedcontrol for said motor, and

the recorded contents of said recording area and the recorded contentsof said different recording area are both reproduced by using the sameoptical pickup.

A further aspect of the invention is an optical disk reproductionapparatus according to the 14th invention, wherein tracking control isnot performed in said different recording area.

A still further aspect of the invention is an optical disk reproductionapparatus according to the 14th invention, wherein tracking control is,in effect, performed in said different recording area.

A yet further aspect of the invention is an optical disk reproductionapparatus according to the 16th invention, wherein a rotational speed isthe rotational speed that would be achieved in said different recordingarea if said rotational phase control were applied.

A still further aspect of the invention is an optical disk reproductionapparatus according to the 14th invention, wherein the rotational speedof said motor in said rotational speed control is maintained at aprescribed value based on a result obtained by measuring aminimum-length pit in said different recording area.

A yet further aspect of the invention is an optical disk reproductionapparatus according to the 14th invention, wherein said low-reflectivityportions are a barcode formed by selectively removing said reflectivefilm.

A still yet further aspect of the invention is an optical diskreproduction apparatus according to the 14th invention whererein

said low-reflectivity portions are a barcode, said different recordingarea is also such area to which contents are recorded with pits, and

when reproducing the recorded contents of said different recording area,a high-frequency-component signal generated during reproduction of saidpits which are formed in said different recording area is reduced oreliminated by a low-pass filter, thereby making it possible to separatea signal which is reproduced from said barcode.

One aspect of the invention is an optical disk reproduction apparatusaccording to the 14th invention, wherein

said low-reflectivity portions are a barcode, and

when reproducing the recorded contents of said different recording area,the width of a signal obtained by reading said barcode is increased to aprescribed width and then measured with sampling pulses from a controlsection.

Another aspect of the invention is an optical disk reproductionapparatus according to any one of inventions from 14th to 21st, whereinsaid optical disk is constructed from two disk-substrates laminatedtogether.

Still another aspect of the invention is an optical disk reproductionapparatus according to the 14th invention, wherein said optical diskincludes a control data area for holding therein physical featureinformation concerning said optical disk, and an identifier forindicating the presence or absence of said barcode is recorded in saidcontrol data area.

Yet another aspect of the invention is an optical disk reproductionapparatus according to claim 23, wherein, after reading recordedcontents of said control data area and judging the presence or absenceof said barcode, it is determined whether an optical pickup should bemoved to an inner portion or an outer portion of said optical disk.

Still yet another aspect of the invention is a marking forming apparatuswhich comprises:

marking forming means for applying a marking on a reflective film formedon a disk;

marking position detecting means for detecting a position of saidmarking; and

position information writing means for converting at least said detectedposition information or information concerning said position informationinto a barcode, and for selectively removing said reflective film towrite said barcode to an optical disk on which data is recorded withCLV,

wherein all or part of said barcode is written in overwriting fashion toa prescribed region of a pre-pit signal area on said optical disk.

A further aspect of the invention is a marking forming apparatusaccording to the 25th invention, wherein said disk is constructed fromtwo disk-substrates laminated together.

A still further aspect of the invention is a marking forming meansaccording to the 25th invention, wherein said position informationwriting means includes encrypting means for encrypting at least saiddetected position information or information concerning said positioninformation, and writes contents thus encrypted to said disk.

A yet further aspect of the invention is a marking forming apparatusaccording to the 25th invention, wherein said position informationwriting means includes digital signature means for applying a digitalsignature to at least said detected position information or informationconcerning said position information,

and the writing at least said detected position information orinformation concerning said position information means writinginformation concerning a result of said digital signature application tosaid disk.

A still yet further aspect of the invention is a reproduction apparatuswhich comprises:

position information reading means for reading position information of amarking or information concerning said position information, saidposition information or said information being formed by (1) applying amarking on a reflective film formed on a disk, (2) detecting position ofthe marking, (3) converting detected said position information or saidinformation into a barcode, and (4) writing the barcode with selectivelyremoving said reflective film on said optical disk on which data isrecorded with CLV;

marking reading means for reading information concerning a physicalposition of said marking;

comparing/judging means for performing comparison and judgement by usinga result of reading by said position information reading means and aresult of reading by said marking reading means; and

reproducing means for reproducing data recorded on said optical disk inaccordance with a result of the comparison and judgement performed bysaid comparing/judging means,

wherein all or part of said barcode is written in overwriting fashion toa prescribed region of a pre-pit signal area on said optical disk.

One aspect of the invention is a reproduction apparatus according to the29th invention, wherein at least said detected position information orinformation concerning said position information is written to said diskby position information writing means.

Another aspect of the invention is a reproduction apparatus according tothe 30th invention, wherein

said position information writing means includes encrypting means forencrypting at least said detected position information or informationconcerning said position information, and

said position information reading means includes decrypting meanscorresponding to said encrypting means, and by using said decryptingmeans, decrypts said encrypted position information or informationconcerning said position information.

Still another aspect of the invention is a reproduction apparatusaccording to the 30th invention, wherein

said position information writing means includes digital signature meansfor applying a digital signature to at least said detected positioninformation or information concerning said position information, andwrites information concerning a result of said digital signatureapplication to said disk,

and said position information reading means includes

authenticating means corresponding to said digital signature means, and

position information extracting means for obtaining said positioninformation from an authentication process performed by saidauthenticating means and/or from said information concerning the resultof said digital signature application,

when an output indicating correctness of said authentication result isproduced from said authenticating means, said comparing/judging meansperforms the comparison and judgement by using the position informationobtained by said position information extracting means and the result ofreading by said marking reading means, and when said output indicatingcorrectness is not produced, the reproduction is not performed.

Yet another aspect of the invention is a method of manufacturing a disk,which comprises the steps of:

forming at least one disk;

forming a reflective film to said formed disk;

applying at least one marking to said reflective film;

detecting at least one position of said marking; and

encrypting said detected position information and writing said encryptedinformation onto said disk,

wherein, when encrypting and writing, at least said encryptedinformation is converted into a barcode, and said barcode is written byselectively removing said reflective film on said disk on which data isrecorded with CLV, and all or part of said barcode is written inoverwriting fashion to a prescribed region of a pre-pit signal area onsaid disk.

Still yet another aspect of the invention is a method of manufacturing adisk, which comprises the steps of:

forming at least one disk;

forming a reflective film to said formed disk;

applying at least one marking to said reflective film;

detecting at least one position of said marking; and

applying a digital signature to said detected position information andwriting onto said disk,

wherein, when applying said digital signature and writing, at least aresult of said digital signature is converted into a barcode, and saidbarcode is written by selectively removing said reflective film on saiddisk on which data is recorded with CLV, all or part of said barcodebeing written in overwriting fashion to a prescribed region of a pre-pitsignal area on said disk.

A further aspect of the invention is a disk wherein a marking is formedby a laser to a reflective film of said disk holding data writtenthereon, at least position information of said marking or informationconcerning said position information is encrypted or applied a digitalsignature, at least said encrypted information or digitalsignature-appended information is converted into a barcode, and saidbarcode is written by selectively removing said reflective film on saiddisk on which data is recorded with CLV, all or part of said barcodebeing written in overwriting fashion to a prescribed region of a pre-pitsignal area on said disk.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a diagram showing a disk manufacturing process and a secondaryrecording process according to the present embodiment;

FIG. 2(a) is a top plan view of a disk according to the embodiment, (b)is a top plan view of the disk according to the embodiment, (c) is a topplan view of the disk according to the embodiment, (d) is a transversesectional view of the disk according to the embodiment, and (e) is awaveform diagram of a reproduced signal according to the embodiment;

FIG. 3 is a flowchart illustrating a process of recording encryptedposition information on a disk in the form of a barcode according to thepresent embodiment;

FIG. 4 is a diagram showing a disk fabrication process and a secondaryrecording process (part 1) according to the present embodiment;

FIG. 5 is a diagram showing the disk fabrication process and thesecondary recording process (part 2) according to the presentembodiment;

FIG. 6 is a diagram showing a two-layer disk fabrication process(part 1) according to the present embodiment;

FIG. 7 is a diagram showing the two-layer disk fabrication process (part2) according to the present embodiment;

FIG. 8(a) is an enlarged view of a nonreflective portion of a laminatedtype according to the present embodiment, and (b) is an enlarged view ofa nonreflective portion of a single-plate type according to the presentembodiment;

FIG. 9(a) is a reproduced-waveform diagram for a nonreflective portionaccording to the present embodiment, (b) is a reproduced-waveformdiagram for a nonreflective portion according to the present embodiment,(c) is a reproduced-waveform diagram for a nonreflective portionaccording to the present embodiment, and (d) is a plan view of a masterdisk produced by a master disk method;

FIG. 10(a) is a cross-sectional view of a nonreflective portion of thelaminated type according to the present embodiment, and (b) is across-sectional view of a nonreflective portion of the single-plate typeaccording to the present embodiment;

FIG. 11 is a schematic diagram, based on an observation through atransmission electron microscope, illustrating a cross section of thenonreflective portion according to the present embodiment;

FIG. 12(a) is a cross-sectional view of a disk according to the presentembodiment, and (b) is a crosssectional view of the nonreflectiveportion of the disk according to the present embodiment;

FIG. 13(a) is a diagram showing a physical arrangement of addresses on alegitimate CD according to the embodiment, and (b) is a physicalarrangement of addresses on an illegally duplicated CD according to theembodiment;

FIG. 14(a) is a diagram showing part (b) of FIG. 33 in further detail,(b) is a diagram showing an equivalent data structure for ECCencoding/decoding, (c) is a diagram showing a mathematical equation forEDC computation, and (d) is a diagram showing a mathematical equationfor ECC computation;

FIG. 15 is a block diagram of a low-reflectivity position detectoraccording to the embodiment;

FIG. 16 is a diagram illustrating the principle of detectingaddress/clock positions of a low-reflectivity portion according to theembodiment;

FIG. 17 is a diagram showing a comparison of low-reflectivity portionaddress tables for a legitimate disk and a duplicated disk;

FIG. 18A is a flowchart illustrating a procedure for encryption, etc.using an RSA function according to the embodiment;

FIG. 18B is a flowchart illustrating a position information checkprocess according to the embodiment;

FIG. 19 is a flowchart illustrating a low-reflectivity positiondetecting program according to the embodiment;

FIG. 20 is a diagram showing a detected waveform of a first-layermarking signal according to the present embodiment;

FIG. 21 is a diagram showing a detected waveform of a second-layermarking signal according to the present embodiment;

FIG. 22 is a flowchart illustrating the function of a scrambleidentifier and the switching between drive ID and disk ID in a programinstallation process according to the present embodiment.

FIG. 23 is a block diagram of a stripe recording apparatus according tothe embodiment;

FIG. 24 is a diagram showing a signal waveform and a trimming pattern inRZ recording according to the embodiment;

FIG. 25 is a diagram showing a signal waveform and a trimming pattern inNRZ recording;

FIG. 26 is a diagram showing a signal waveform and a trimming pattern inPE-RZ recording according to the embodiment;

FIG. 27 is a diagram showing a top plan view of disk stripes, along withsignal waveforms, according to the embodiment;

FIG. 28(a) is a perspective view of a converging unit according to theembodiment, and (b) is a diagram showing a stripe arrangement and anemitting-pulse signal;

FIG. 29(a) is a perspective view of the converging unit, with a beamdeflector appended thereto, according to the embodiment, and (b) is adiagram showing a stripe arrangement and an emitting-pulse signal;

FIG. 30 is a diagram showing the arrangement of stripes on a disk andthe contents of control data according to the embodiment;

FIG. 31 is a flowchart illustrating how control mode is switched betweenCAV and CLV when playing back stripes according to the embodiment;

FIG. 32 is a diagram showing a stripe area and an address area on a diskaccording to the embodiment;

FIG. 33(a) is a diagram showing a data structure after ECC encodingaccording to the embodiment, (b) is a diagram showing a data structureafter ECC encoding according to the embodiment (when n=1), and (c) is adiagram showing an ECC error-correction capability according to theembodiment;

FIG. 34 is a diagram showing the data structure of a synchronizationcode;

FIG. 35(a) is a diagram showing the configuration of an LPF, and (b) isa diagram showing a waveform filtered through the LPF;

FIG. 36(a) is a diagram showing a reproduced signal waveform accordingto the embodiment, and (b) is a diagram for explaining a dimensionalaccuracy of a stripe according to the embodiment;

FIG. 37 is a diagram showing a synchronization code and a laser emittingpulse signal waveform;

FIG. 38 is a diagram showing a procedure for reading control data forplayback according to the embodiment;

FIG. 39 is a diagram showing a top plan view of a disk having apinhole-like optical marking as a physical feature according to theembodiment;

FIG. 40 is a diagram showing a procedure for playing back a PCA area ina tracking ON condition according to the embodiment;

FIG. 41 is a block diagram of a playback apparatus implementingrotational speed control according to the embodiment;

FIG. 42 is a block diagram of a playback apparatus implementingrotational speed control according to the embodiment;

FIG. 43 is a block diagram of a playback apparatus implementingrotational speed control according to the embodiment;

FIG. 44 is a diagram illustrating a piracy prevention algorithmaccording to the embodiment;

FIG. 45 is a diagram for explaining barcode encryption according to theembodiment;

FIG. 46 is a diagram showing another application example of the barcodeaccording to the embodiment;

FIG. 47 is a perspective view showing a nonreflective portion formed ina two-layer disk according to the embodiment; and

FIG. 48 is a diagram showing a comparison of address coordinatepositions on different master disks according to the embodiment.

DESCRIPTION OF THE REFERENCE NUMERALS

584. LOW-REFLECTIVITY PORTION, 586. LOW REFLECTIVITY LIGHT AMOUNTDETECTOR, 587. LIGHT AMOUNT LEVEL COMPARATOR, 588. LIGHT AMOUNTREFERENCE VALUE, 599. LOW REFLECTIVITY PORTION START/END POSITIONDETECTOR, 600 LOW-REFLECTIVITY PORTION POSITION DETECTOR, 601.LOW-REFLECTIVITY PORTION ANGULAR POSITION SIGNAL OUTPUT SECTION, 602.LOW-REFLECTIVITY PORTION ANGULAR POSITION DETECTOR, 605.LOW-REFLECTIVITY PORTION START POINT, 606. LOW-REFLECTIVITY PORTION ENDPOINT, 607. TIME DELAY CORRECTOR, 816. DISK MANUFACTURING PROCESS, 817.SECONDARY RECORDING PROCESS, 818. DISK MANUFACTURING PROCESS STEPS, 819.SECONDARY RECORDING PROCESS STEPS, 820. SOFTWARE PRODUCTION PROCESSSTEPS, 830. ENCODING MEANS, 831. PUBLIC KEY ENCRYPTION, 833. FIRSTSECRET KEY, 834. SECOND SECRET KEY, 835. COMBINING SECTION, 836.RECORDING CIRCUIT, 837. ERROR-CORRECTION ENCODER, 838. REED-SOLOMONENCODER, 839. INTERLEAVER, 840. PULSE INTERVAL MODULATOR, 841. CLOCKSIGNAL GENERATOR, 908. ID GENERATOR, 909. INPUT SECTION, 910. RZMODULATOR, 913. CLOCK SIGNAL GENERATOR, 915. MOTOR, 915. ROTATIONSENSOR, 916. COLLIMATOR, 917. CYLINDRICAL LENS, 918. MASK, 919.CONVERGING LENS, 920. FIRST TIME SLOT, 921. SECOND TIME SLOT, 922. THIRDTIME SLOT, 923. STRIPE, 924. PULSE, 925. FIRST RECORDING REGION, 926.SECOND RECORDING REGION, 927. ECC ENCODER, 928. ECC DECODER, 929. LASERPOWER SUPPLY CIRCUIT, 930. STEPS (IN CAV PLAYBACK FLOWCHART), 931. BEAMDEFLECTOR, 932. SLIT, 933. STRIPE, 934. SUB-STRIPE, 935. DEFLECTIONSIGNAL GENERATOR, 936. CONTROL DATA AREA, 937. STRIPE PRESENCE/ABSENCEIDENTIFIER, 938. ADDITIONAL STRIPE PORTION, 939. ADDITIONAL STRIPEPRESENCE/ABSENCE IDENTIFIER, 940. STEPS (FOR STRIPE PRESENCE/ABSENCEIDENTIFIER PLAYBACK FLOWCHART), 941. OPTICAL MARKING (PINHOLE), 942.PE-RZ DEMODULATOR, 943. LPF, 944. ADDRESS AREA, 945. MAIN BEAM, 946.SUB-BEAM, 948. STRIPE REVERSE-SIDE RECORD IDENTIFIER, 949. STRIPE GAPPORTION, 950. SCANNING MEANS, 951. DATA ROW, 952. ECC ROW, 953.EDGE-SPACING DETECTING MEANS, 954. COMPARING MEANS, 955. MEMORY MEANS,956. OSCILLATOR, 957. CONTROLLER, 958. MOTOR DRIVE CIRCUIT, 959. BARCODEREADING MEANS, 963. MODE SWITCH, 964. HEAD MOVING MEANS, 965. FREQUENCYCOMPARATOR, 966. OSCILLATOR, 967. FREQUENCY COMPARATOR, 968. OSCILLATOR,969. MOTOR

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The preferred embodiments of the present invention will be describedbelow with reference to the accompanying drawings. In the descriptionhereinafter given, position information for piracy prevention, which isa form of ID, is taken as an example of information to be barcoded.

In the first-half part (I) of the description, a detailed explanationwill be given of the piracy prevention position information as a form ofID, followed by a brief explanation of how the information is convertedinto a barcode to complete an optical disk and how the optical disk isplayed back. In the second-half part (II), the technique for barcodingthe piracy prevention position information will be described in furtherdetail and in a concrete manner. More specifically, the first-half part(I) deals with (A) Manufacturing a disk, (B) Forming a marking by usinglaser light, (C) Reading the position information of the marking, (D)Encrypting the position information, converting the encrypted positioninformation into a barcode, and writing the barcode in a pre-pit area ofthe optical disk in overwriting fashion, and (E) Playing back theoptical disk on a player. The second-half part (II) first describes (A)Usefulness of the barcode for a laminated-type optical disk, thenproceeds to (B) Barcoding the position information of the marking as adisk-unique ID, (C) Features of the barcode-recorded optical diskformat, methods of tracking control, and methods of rotational speedcontrol during reading of the barcode, and (D) Playing back thebarcode-recorded optical disk. The second-half part (II) further dealsin detail with (E) Manufacturing techniques for implementing the barcoderecording method, followed by a brief explanation of a barcode playbackapparatus (player). Finally, a description is given of (F) An example ofthe above barcode encryption and another application example of thebarcode.

(I)

Before proceeding to the description of the above (A) to (E), we willfirst describe a general process flow from disk manufacturing to thecompletion of an optical disk by using the flowchart of FIG. 1.

In this patent specification, laser trimming is also referred to aslaser marking, while a nonreflective optical marking portion is simplyreferred to as the barcode, stripe, marking, or optical marking or,sometimes, as the physical ID unique to a disk.

First, the software company performs software authoring in softwareproduction process 820. The completed software is delivered from thesoftware company to the disk manufacturing factory. In diskmanufacturing process 816 at the disk manufacturing factory, thecompleted software is input in step 818a, a master disk is produced(step 818b), disks are pressed (steps 818e, 818g), reflective films areformed on the respective disks (steps 818f, 818h), the two disks arelaminated together (step 818i), and a ROM disk such as a DVD or CD iscompleted (step 818m, etc.).

The thus completed disk 800 is delivered to the software maker or to afactory under control of the software maker, where, in secondaryrecording process 817, an anti-piracy marking 584, such the one shown inFIG. 2, is formed (step 810a), and accurate position information of thismark is read by a measuring means (step 819b) to obtain the positioninformation which serves as the physical feature information of thedisk. This physical feature information of the disk is encrypted in step819c. The encrypted information is converted to a PE-RZ-modulated signalwhich is then recorded in step 819d as a barcode signal on the disk byusing a laser. The disk physical feature information may be combinedtogether with software feature information for encryption in step 819c.

The above processes will be described in further detail. That is, a diskfabrication process, a marking formation process, a marking positionreading process, and an encrypted information writing process for anoptical disk according to the present invention will be described indetail with reference to FIGS. 4 and 5 and FIGS. 8 to 12. Asupplementary explanation will also be given dealing with a disk havingtwo reflective layers with reference to FIGS. 6 and 7. In the followingdescription, the marking formation process and the marking positionreading process are collectively called the secondary recording process.

(A) First, the disk fabrication process will be described. In the diskfabrication process 806 shown in FIG. 4, first a transparent substrate801 is pressed in step (1). In step (2), a metal such as aluminum orgold is sputtered to form a reflective layer 802. An adhesive layer 804formed from an ultraviolet curing resin is applied by spin coating to asubstrate 803 formed in a different processing step, and the substrate803 is bonded to the transparent substrate 801 having the reflectivelayer 802, and they are rotated at high speed to make the bondingspacing uniform. By exposure to external ultraviolet radiation, theresin hardens, thus firmly bonding the two substrates together. In step(4), a printed layer 805 where a CD or DVD title is printed, is printedby screen printing or offset printing. Thus, in step (4), the ordinarylaminated-type optical ROM disk is completed.

(B) Next, the marking formation process will be described with referenceto FIGS. 4 and 5. In FIG. 4, a laser beam from a pulsed laser 813 suchas a YAG laser is focused through a converging lens 814 onto thereflective layer 802, to form a nonreflective portion 815 as shown instep (6) in FIG. 5. That is, a distinct waveform, such as the waveform(A) shown in step (7), is reproduced from the nonreflective portion 815formed in step (6) in FIG. 5. By slicing this waveform, a markingdetection signal such as shown by waveform (B) is obtained, from whichhierarchial marking position information comprising an address, such asshown in signal (d), and an address, a frame synchronizing signalnumber, and a reproduced clock count, such as shown in signal (e), canbe measured.

At the rising edge of the thus obtained marking detection signal, aspecific address (indicated by address n in FIG. 5(d)) is read by theoptical pickup from within the plurality of addresses shown in FIG.5(d). FIG. 5(b) shows the physical location of the specific address inschematic form. On the other hand, FIG. 5(e) shows the logical structureof the data. As shown in FIG. 5(e), there are m frame synchronizationsignals under address n, and k reproduced clock pulses under each framesynchronization signal. Therefore, the position of the marking measuredby the optical pickup can be represented by address, framesynchronization signal number, and reproduced clock count.

As previously stated, a supplementary explanation will be given below ofan alternative type of disk (a two-layer laminated disk) with referenceto FIGS. 6 and 7.

FIGS. 4 and 5 showed a disk generally known as a single-layer laminateddisk which has a reflective layer only on one substrate 801. On theother hand, FIGS. 6 and 7 show a disk generally known as a two-layerlaminated disk which has reflective layers on both substrates 801 and803. For laser trimming, the processing steps (5) and (6) arefundamentally the same for both types of disks, except with significantdifferences which are briefly described below. First, while thesingle-layer disk uses a reflective layer formed from an aluminum filmhaving reflectivity as high as 70% or over, in the two-layer disk thereflective layer 801 formed on the reading-side substrate 801 is asemi-transparent gold (Au) film having a reflectivity of 30%, while thereflective layer 802 formed on the print-side substrate 803 is the sameas that used in the single-layer disk. Second, as compared with thesingle-layer disk, the two-layer disk is required to have high opticalaccuracy; for example, the adhesive layer 804 must be opticallytransparent and be uniform in thickness, and the optical transparencymust not be lost due to laser trimming.

Parts (7), (8), and (9) of FIG. 7 show the signal waveforms obtainedfrom the first layer of the two-recording-layer disk. Likewise, parts(10), (11), and (12) of FIG. 7 show the signal waveforms obtained fromthe second layer of the two-recording-layer disk. The contents of thesesignal waveforms are essentially the same as those of the waveformsdescribed with reference to parts (a) to (c) of FIG. 5. The waveformfrom the second layer is similar to that from the first layer, thoughthe signal level is lower than from the first layer. However, since thefirst and second layers are bonded together, relative positionalaccuracy between them is random and can be controlled only with anaccuracy of a few hundred microns. As will be described later, since thelaser beam passes through the two reflective films, to make an illegaldisk the position informations on the first and second layers for thefirst mark, for example, have to be made to match the same value on thelegitimate disk. But making them match would require a near-submicronaccuracy in laminating, and consequently, making illegal disks of thetwo-layer type is practically impossible.

The technique for forming the nonreflective optical marking portion willbe described in further detail in sections (a) to (d) below withreference to FIGS. 8 to 12, etc., dealing with the laminated type incomparison with a single-plate type. FIGS. 8(a) and (b) are micrographsshowing plan views of nonreflective optical marking portions, and FIG.10(a) is a simplified schematic crosssectional view of a nonreflectiveportion of the two-layer laminated disk. (a) Using a 5 μj/pulse YAGlaser, a laser beam was applied to a 500 angstrom aluminum layer lying0.6 mm below the surface of a 1.2 mm thick ROM disk consisting of two0.6 mm thick disks laminated together, and, as a result, a 12 μm wideslit-like nonreflective portion 815 was formed, as shown in the X 750micrograph of FIG. 8(a). In this X 750 micrograph, no aluminum residueswere observed on the nonreflective portion 815. Thick swollen aluminumlayers, 2000 angstroms thick and 2 μm wide, were observed alongboundaries between the nonreflective portion 815 and reflectiveportions. As shown in FIG. 10(a), it was confirmed that no significantdamage had occurred inside. In this case, the application of the pulsedlaser presumably melted the aluminum reflective layer, causing aphenomenon of molten aluminum buildup along the boundaries on both sidesdue to the surface tension. We call this a hot melt surface tension(HMST) recording method. This is a characteristic phenomenon observedonly on a laminated disk 800. FIG. 11 is a schematic diagram, based onan observation through a transmission electron microscope (TEM),illustrating a cross section of the nonreflective portion formed by theabove laser trimming process. And FIG. 11 shows that the adhesive layerof the disk has been removed by using solvent.

In the figure, if the aluminum film swollen portion is 1.3 μm wide and0.20 μm thick, the amount of increased aluminum in that portion is1.3×(0.20-0.05)=0.195 μm². The amount of aluminum originally depositedin a half portion (5 μm) of the laser exposed region (10 μm) was5×0.05=0.250 μm². The difference is calculated as 0.250-0.195=0.055 μm².In terms of length, this is equivalent to 0.055/0.05=1.1 μm. This meansthat an aluminum layer of 0.05 μm thickness and 1.1 μm length remained,and therefore, it can be safely said that almost all aluminum was drawnto the film swollen portion. Thus, the result of the analysis of thefigure also verifies the explanation about the above-describedcharacteristic phenomenon.

(b) We will next deal with the case of a single-plate optical disk (anoptical disk comprising a single disk). An experiment was conducted byapplying laser pulses of the same power to a 0.05 μm thick aluminumreflective film formed on a single-sided molded disk, of which result isshown in FIG. 8(b). As shown in the figure, aluminum residues wereobserved, and since these aluminum residues cause reproduction noise, itcan be seen that the single-plate type is not suitable for secondaryrecording of optical disk information of which a high density and a lowerror rate are demanded. Furthermore, unlike the laminated disk, in thecase of the single-plate disk, the protective layer 862 is inevitablydamaged, as shown in FIG. 10(b), when the nonreflective portion issubjected to laser trimming. The degree of damage depends on the laserpower, but the damage cannot be avoided even if the laser power iscontrolled accurately. Moreover, according to our experiment, theprinted layer 805 formed by screen printing to a thickness of a fewhundred microns on the protective layer 862 was damaged when its thermalabsorptance was high. In the case of the single-plate disk, to addressthe problem of protective layer damage, either the protective layer hasto be applied once again or the laser cut operation should be performedbefore depositing the protective layer. In any case, the single-platetype may present a problem in that the laser cut process has to beincorporated in the pressing process. This limits the application of thesingle-plate disk despite its usefulness.

(c) A comparison between single-plate disk and laminated disk has beendescribed above, using a two-layer laminated disk as an example. As isapparent from the above description, the same effect as obtained withthe two-layer laminated disk can be obtained with the single-layerlaminated disk. Using FIGS. 12(a), 12(b), etc., a further descriptionwill be given dealing with the single-layer laminated disk type. Asshown in FIG. 12(a), the reflective layer 802 has the transparentsubstrate 801 of polycarbonate on one side, and the hardened adhesivelayer 804 and a substrate on the other side, the reflective layer 802thus being hermetically sealed therebetween. In this condition, pulsedlaser light is focused thereon for heating; in the case of ourexperiment, heat of 5 μJ/pulse is applied to a circular spot of 10 to 20μm diameter on the reflective layer 802 for a short period of 70 ns. Asa result, the temperature instantly rises to 600° C., the melting point,melting state is caused. By heat transfer, a small portion of thetransparent substrate 801 near the spot is melted, and also a portion ofthe adhesive layer 804 is melted. The molted aluminum in this state iscaused by surface tension to build up along boundaries 821a and 821b,with tension being applied to both sides, thus forming buildups 822a and822b of hardened aluminum, as shown in FIG. 12(b). The nonreflectiveportion 584 free from aluminum residues is thus formed. This shows thata clearly defined nonreflective portion 584 can be obtained bylaser-trimming the laminated disk as shown in FIGS. 10(a) and 12(a).Exposure of the reflective layer to the outside environment due to adamaged protective layer, which was the case with the single-plate type,was not observed even when the laser power was increased more than 10times the optimum value. After the laser trimming, the nonreflectivelayer 584 has the structure shown in FIG. 12(b) where it is sandwichedbetween the two transparent substrates 801, 803 and sealed with theadhesive layer 804 against the outside environment, thus producing theeffect of protecting the structure from environmental effects.

(d) Another benefit of laminating two disks together will be describednext. When secondary recording is made in the form of a barcode, anillegal manufacturer can expose the aluminum layer by removing theprotective layer in the case of a single-plate disk, as shown in FIG.10(b). This gives rise to a possibility that nonecrypted data may betampered with by redepositing an aluminum layer over the barcode portionon a legitimate disk and then laser-trimming a different barcode. Forexample, if the ID number is recorded in plaintext or separately frommain ciphertext, in the case of a single-plate disk it is possible toalter the ID number, enabling illegal use of the software by using adifferent password. However, if the secondary recording is made on thelaminated disk as shown in FIG. 10(a), it is difficult to separate thelaminated disk into two sides. In addition, when removing one side fromthe other, the aluminum reflective film is partially destroyed. Then theanti-piracy marking is destroyed, the disk will be judged as being apirated disk and will not run. Accordingly, when making illegalalterations to the laminated disk, the yield is low and thus illegalalterations are suppressed for economic reasons. Particularly, in thecase of the two-layer laminated disk, since the polycarbonate materialhas temperature/humidity expansion coefficients, it is nearly impossibleto laminate the two disks, once separated, by aligning the anti-piracymarkings on the first and second layers with an accuracy of a fewmicrons, and to mass produce disks. Thus, the two-layer type provides agreater effectiveness in piracy prevention. It was thus found that aclearly defined slit of a nonreflective portion 584 can be obtained bylaser-trimming the laminated disk 800.

The technique for forming the nonreflective optical marking portion hasbeen described in (a) to (d) above.

(C) Next, the process of reading the position of the thus formed markingwill be described.

FIG. 15 is a block diagram showing a low reflectivity light amountdetector 586 for detecting the nonreflective optical marking portion,along with its adjacent circuitry, in an optical disk manufacturingprocess. FIG. 16 is a diagram illustrating the principle of detectingaddress/clock positions of the low reflectivity portion. For convenienceof explanation, the following description deals with the operatingprinciple when a read operation is performed on a nonreflective portionformed on an optical disk constructed from a single disk. It will berecognized that the same operating principle also applies to an opticaldisk constructed from two disks laminated together.

As shown in FIG. 15, the disk 800 is loaded into a marking readingapparatus equipped with a low reflectivity position detector 600 to readthe marking, and in this case, since a signal waveform 823 due to thepresence and absence of pits and a signal waveform 824 due to thepresence of the nonreflective portion 584 are significantly different insignal level, as shown in the waveform diagram of FIG. 9(a), they can beclearly distinguished using a simple circuit.

FIG. 9(a) is a diagram showing the waveform of a playback signal from aPCA area, described later, containing the nonreflective portion 584formed by laser light. FIG. 9(b) is a diagram showing the waveform ofFIG. 9(a) but with a different time axis.

By removing the reflective film by laser light, as described above, awaveform easily distinguishable from that of a pit signal is obtained.Rather than forming an anti-piracy identification mark by removing thereflective film by laser light, as described above, the anti-piracy markmay be formed by changing the shape of pits on the master disk. Thismethod will be described below. FIG. 9(c) shows the waveform of aplayback signal when the anti-piracy identification mark was formed bymaking pits longer than other data pits on the master disk. It can beseen from the diagram that the waveform 824p of the anti-piracyidentification mark is distinguishable from the waveform of other pitdata. In this way, a waveform similar to that obtained from the PCA areadescribed later can be obtained by forming longer pits on the masterdisk; in this case, however, the waveform is a little difficult todistinguish as compared to the waveforms shown in parts (a) and (b) ofFIG. 9.

By removing the reflective film by laser light, as described above, awaveform easily distinguishable from that of a pit signal is obtained.Rather than forming the barcode of the invention by removing thereflective film by laser light, as described above, the barcode may beformed by changing the shape of pits on the master disk. This masterdisk method will be described below. FIG. 9(d) is a plan view showing aportion of a master disk wherein pits 824q in a few hundred tracks onthe master disk are made longer than other data pits and made equal tothe barcode bar width t (=10 μm). Since reflectivity drops in thislonger-bit area, a waveform 824p as shown in FIG. 9(c) is obtained. Itcan be seen from the diagram that the waveform 824p by the master diskmethod is distinguishable from the waveform of other pit data. In thisway, a waveform similar to that obtained from the PCA area describedlater can be obtained by the master disk method; in this case, however,the waveform is a little difficult to distinguish as compared to thewaveforms shown in parts (a) and (b) of FIG. 9.

As shown in FIG. 16(1), the start and end positions of the nonreflectiveportion 564 having the above waveform can be easily detected by the lowreflectivity light amount detector 586 shown in the block diagram ofFIG. 15. Using the reproduced clock signal as the reference signal,position information is obtained in a low reflectivity positioninformation output section 596. FIG. 16(1) shows a cross-sectional viewof the optical disk.

As shown in FIG. 15, a comparator 587 in the low reflectivity lightamount detector 586 detects the low reflectivity light portion bydetecting an analog light reproduced signal having a lower signal levelthan a light amount reference value 588. During the detection period, alow reflectivity portion detection signal of the waveform shown in FIG.16(5) is output. The addresses and clock positions of the start positionand end position of this signal are measured.

The reproduced light signal is waveshaped by a waveform shaping circuit590 having an AGC 590a, for conversion into a digital signal. A clockregenerator 38a regenerates a clock signal from the waveshaped signal.An EFM demodulator 592 in a demodulating section 591 demodulates thesignal, and an ECC corrects errors and outputs a digital signal. TheEFMdemodulated signal is also fed to a physical address output section593 where an address of MSF, from Q bits of a subcode in the case of aCD, is output from an address output section 594 and a synchronizingsignal, such as a frame synchronizing signal, is output from asynchronizing signal output section 595. From the clock regenerator 38a,a demodulated clock is output.

In a low reflectivity portion address/clock signal position signaloutput section 596, a low reflectivity portion start/end positiondetector 599 accurately measures the start posistion and end position ofthe low reflectivity portion 584 by using an (n-1) address outputsection 597 and an address signal as well as a clock counter 598 and asynchronizing clock signal or the demodulated clock. This method will bedescribed in detail by using the waveform diagrams shown in FIG. 16. Asshown in the cross-sectional view of the optical disk in FIG. 16(1), thelow reflectivity portion 584 of mark number 1 is formed partially. Areflection selope signal such as shown in FIG. 16(3), is output, thesignal level from the reflective portion being lower than the lightamount reference value 588. This is detected by the light levelcomparator 587, and a low reflectivity light detection signal, such asshown in FIG. 16(5), is output from the low reflectivity light amountdetector 586. As shown by a reproduced digital signal in FIG. 16(4), nodigital signal is output from the mark region since it does not have areflective layer.

Next, to obtain the start and end positions of the low reflectivitylight detection signal, the demodulated clock or synchronizing clockshown in FIG. 16(6) is used along with address information. First, areference clock 605 at address n in FIG. 16(7) is measured. When theaddress immediately preceding the address n is detected by the (n-1)address output section 597, it is found that the next sync 604 is a syncat address n. The number of clocks from the synch 604 to the referenceclock 605, which is the start position of the low reflectivity lightdetection signal, is counted by the clock counter 598. This clock countis defined as a reference delay time TD which is measured by a referencedelay time TD measuring section 608 for storage therein.

The circuit delay time varies with reproduction apparatus used forreading, which means that the reference delay time TD varies dependingon the reproduction apparatus used. Therefore, using the TD, a timedelay corrector 607 applies time correction, and the resulting effect isthat the start clock count for the low reflectivity portion can bemeasured accurately if reproduction apparatus of different designs areused for reading. Next, by finding the clock count and the start and endaddresses for the optical mark No. 1 in the next track, clock m+14 ataddress n+12 is obtained, as shown in FIG. 16(8). Since TD=m+2, theclock count is corrected to 12, but for convenience of explanation, n+14is used. We will describe another method, which eliminates the effectsof varying delay times without having to obtain the reference delay timeTD in the reproduction apparatus used for reading. This method can checkwhether the disk is a legitimate disk or not by checking whether thepositional relationship of mark 1 at address n in FIG. 16(8) relative toanother mark 2 matches or not. That is, TD is ignored as a variable, andthe difference between the position, A1=a1+TD, of mark 1 measured andthe position, A2=a2+TD, of mark 2 measured is obtained, which is givenas A1-A2=a1-a2. At the same time, it is checked whether this differencematches the difference, a1-a2, between the position al of the decryptedmark 1 and the position information a2 of the mark 2, thereby judgingwhether the disk is a legitimate disk or not. The effect of this methodis that the positions. can be checked after compensating for variationsof the reference delay time TD by using a simpler constitution.

(D) Next, the encrypted information writing process will be described.The position information read in the process (C) is first converted intociphertext or "signed" with a digital signature. Then, the markingposition information thus encrypted or signed is converted into abarcode as an ID unique to the optical disk, and the barcode is recordedin overwriting fashion in a prescribed region of a pre-pit area on theoptical disk. Barcode patterns 584c-584e in FIG. 2(a) indicate thebarcode written to the prescribed region of the pre-pit area, that is,in the innermost portion of the pre-pit area.

Parts (1) to (5) of FIG. 3 show the process from the recording of thebarcode to the demodulation of the barcode detection signal by a PE-RZmodulated signal demodulator. In part (1) of FIG. 3, the reflectivelayer is trimmed by a pulsed laser, and a barcode-like trimming pattern,such as shown in part (2) of the figure, is formed. At the playbackapparatus (player), an envelope waveform some portions of which aremissing, as shown in part (3) of the figure, is obtained. The missingportions result in the generation of a low level signal that cannotoccur with a signal generated from an ordinary pit. Therefore, thissignal is sliced by a second slice level comparator to obtain alow-reflectivity portion detection signal as shown in part (4) of thefigure. In part (5) of the figure, the playback signal of the barcode isdemodulated from this low-reflectivity portion detection signal by thePE-RZ modulated signal demodulator 621 which will be described in detailin the second-half part (II). It will be appreciated that, instead ofthe PE-RZ modulated signal demodulator 621, a pulse-width modulatedsignal demodulator (PWM demodulator) may be used, in which case also, asimilar effect can be obtained.

When applying the above encryption or digital signature, a secret key ofa public key encryption function is used. As an example of theencryption, FIGS. 18A and 18B show an encryption process using an RSAfunction.

As shown in FIG. 18A, the process consists of the following majorroutines: step 735a where marking position information is measured atthe optical disk maker, step 695 where the position information isencrypted (or a digital signature is appended), step 698 where theposition information is decrypted (or the signature is verified orauthenticated). in the reproduction apparatus, and step 735w where acheck is made to determine whether the disk is a legitimate optical diskor not.

First, in step 735a, the marking position information on the opticaldisk is measured in step 735b. The position information is thencompressed in step 735d, and the compressed position information H isobtained in step 735e.

In step 695, the ciphertext of the compressed position information H isconstructed. First, in step 695, a secret key, d, of 512 or 1024 bits,and secret keys, p and q, of 256 or 512 bits, are set, and in step 695b,encryption is performed using an RSA function. When the positioninformation H is denoted by M, M is raised to d-th power and mod n iscalculated to yield ciphertext C. In step 695d, the ciphertext C isrecorded on the optical disk. The optical disk is thus completed and isshipped (step 735k ).

In the reproduction apparatus, the optical disk is loaded in step 735m,and the ciphertext C is decrypted in step 698. More specifically, theciphertext C is recovered in step 698e, and public keys, e and n, areset in step 698f; then in step b, to decrypt the ciphertext C, theciphertext C is raised to e-th power and the mod n of the result iscalculated to obtain plaintext M. The plaintext M is the compressedposition information H. An error check may be performed in step 698g. Ifno errors, it is decided that no alterations have been made to theposition information, and the process proceeds to the disk check routine735w shown in FIG. 18B. If an error is detected, it is decided that thedata is not legitimate one, and the operation is stopped.

In the next step 736a, the compressed position information H is expandedto recover the original position information. In step 736c, measurementsare made to check whether the marking is actually located in theposition on the optical disk indicated by the position information. Instep 736d, it is checked whether the difference between the decryptedposition information and the actually measured position informationfalls within a tolerance. If the check is OK in step 736e, the processproceeds to step 736h to output software or data or execute programsstored on the optical disk. If the check result is outside thetolerance, that is, if the two pieces of position information do notagree, a display is produced to the effect that the optical disk is anillegally duplicated one, and the operation is stopped in step 736g. RSAhas the effect of reducing required capacity since only the ciphertextneed be recorded.

(E) The processing steps in the optical disk manufacturing process havebeen described above. Next, the constitution and operation of areproduction apparatus (player) for reproducing the thus completedoptical disk on a player will be described with reference to FIG. 44.

In the figure, the construction of an optical disk 9102 will bedescribed first. A marking 9103 is formed on a reflective layer (notshown) deposited on the optical disk 9102. In the manufacturing processof the optical disk, the position of the marking 9103 was detected byposition detecting means, and the detected position was encrypted asmarking position information and written on the optical disk in the formof a barcode 9104.

Position information reading means 9101 reads the barcode 9104, anddecrypting means 9105 contained therein decrypts the contents of thebarcode for output. Marking reading means 9106 reads the actual positionof the marking 9103 and outputs the result. Comparing/judging means 9107compares the decrypted result from the decrypting means 9105 containedin the position information reading means 9101 with the result ofreading by the marking reading means 9106, and judges whether the twoagree within a predetermined allowable range. If they agree, areproduction signal 9108 for reproducing the optical disk is output; ifthey do not agree, a reproduction stop signal 9109 is output. Controlmeans (not shown) controls the reproduction operation of the opticaldisk in accordance with these signals; when the reproduction stop signalis output, an indication to the effect that the optical disk is anillegal duplicated disk is displayed on a display (not shown) and thereproduction operation is stopped. In the above operation, it will berecognized that it is also possible for the marking reading means 9106to use the decrypted result from the decrypting means 9105 when readingthe actual position of the marking 9103.

Namely in this case, the marking reading means 9106 checks whether themarking is actually located in the position on the optical diskindicated by the position information which is decrypted by thedecrypting means 9105.

Thus the reproduction apparatus of the above construction can detect anillegally duplicated optical disk and stop the reproduction operation ofthe disk, and can prevent illegal duplicates practically

(II)

We finish here the description of the first-half part (I), and nowproceed to the description of the second-half part (II). This partfocuses particularly on techniques, including a barcode formationmethod, used when barcoding the above marking position information (IDinformation) as a disk-unique ID.

(A) Features of the optical disk of the present invention will bedescribed.

When a barcode is recorded by laser trimming on the above-describedsingle-plate disk, the protective layer 862 is destroyed, as explainedin connection with FIG. 10(b). Therefore, after laser trimming at apress factory, the destroyed protective layer 862 has to be reformed atthe press factory.

This means that a barcode cannot be recorded on the optical disk at asoftware company or a dealer that does not have the necessary equipment.The problem expected here is that the application of barcode recordingis greatly limited.

On the other hand, when the marking position information was recorded asa barcode by laser trimming on the laminated-type disk of the inventionformed from two transparent substrates laminated together, it wasconfirmed that the protective layer 804 remained almost unchanged, asalready explained in connection with FIG. 10(a). This was confirmed byexperiment by observing the disk under an optical microscope of 800Xmagnification. It was also confirmed that no change had occurred to thereflective film in the trimmed portion after an environmental test of 96hours at a temperature of 85° C. and a humidity of 95%.

In this way, when the laser trimming of the present invention is appliedto a laminated disk such as a DVD, there is no need to reform theprotective layer at the factory. This offers a great advantage in that abarcode can be recorded by trimming on the optical disk at a place otherthan the press factory, for example, at a software company or a dealer.The usefulness of barcode recording on the laminated-type optical diskwas thus confirmed.

In this case, since the secret key information for encryption that thesoftware company keeps need not be delivered to a party outside thecompany, security increases greatly, particularly when securityinformation such as a serial number for copy prevention is recorded as abarcode in addition to the above-described position information.Furthermore, in the case of a DVD, since the barcode signal can beseparated from DVD pit signals by setting the trimming line width at avalue greater than 14T or 1.82 microns, as will be described later, thebarcode signal can be recorded in the pit recording area on the DVD insuperimposing fashion. The barcode formed in this way offers the effectthat the barcode can be read by the optical pickup used to read the pitsignal. This effect can be obtained not only with the laminated-typedisk but also with the previously described single-plate disk.

Thus, by applying the barcode forming method and modulation recordingmethod of the invention to a laminated-type disk such as a DVD, alaminated-type optical disk can be provided that permits secondaryrecording after shipment from the factory. The above description hasdealt mainly with a case in which the barcode is formed by lasertrimming on a laminated-type disk of a two-layer, single-sided structure(with two reflective layers formed on one side). This single-sided,two-layered optical disk is the type of disk that permits playback ofboth sides from one side of the disk without having to turn over thedisk.

On the other hand, when trimming is performed on a double-sided,laminated-type optical disk that needs turning over when playing backthe reverse side, the laser light passes through the two reflectivefilms each formed on one side of the disk. Therefore, the barcode can beformed simultaneously on both sides. This provides an advantage formedia fabrication in that the barcode can be recorded simultaneously onboth sides in a single step.

In this case, when the optical disk is turned over to play back thereverse side on a playback apparatus, the barcode signal is played backin just the opposite direction to the direction that the barcode signalon the front side is played back. μmethod for identifying the reverseside is therefore needed. This will be described in detail later.

(B) Referring now to FIGS. 23 to 26, etc., we will describe theconstruction and operation of an optical disk barcode forming apparatusfor converting the marking position information (ID number) into abarcode as a disk-unique ID and for recording the barcode in aprescribed region of a pre-pit area. A barcode recording method, etc.will also be described.

(a) First, the optical disk barcode recording apparatus will bedescribed with reference to FIG. 23.

FIG. 23 is a diagram showing the configuration of the barcode recordingapparatus for implementing an optical disk barcode forming method in oneembodiment of the present invention. In the above mentioned embodiment,data to be barcoded is the data of encrypted version of marking positioninformation. But the data to be barcode is not restricted to the aboveembodiment. It may include, for example, input data and an ID numberissued from an ID generator 908, as shown in FIG. 23, or any other kindof data.

In FIG. 23, the input data and the ID number issued from the IDgenerator 908 are combined together in an input section 909; in anencryption encoder 830, the combined data is subjected to signature orencryption using an RSA function, etc. as necessary, and in an ECCencoder 907, error-correction coding and interleaving are applied. Theencryption process and the playback process will be described in detaillater by way of example with reference to FIG. 45.

The data is then fed into an RZ modulator 910 where phase-encoding (PE)RZ modulation to be described later is performed. The modulating clockused here is created by a clock signal generator 913 in synchronism witha rotation pulse from a motor 915 or a rotation sensor 915a.

Based on the RZ-modulated signal, a trigger pulse is created in a laseremitting circuit 911, and is applied to a laser 912 such as a YAG laserestablished by a laser power supply circuit 929. The laser 912 thusdriven emits pulsed laser light which is focused through a convergingunit 914 onto the reflective film 802 on the laminated disk 800,removing the reflective film in a barcode pattern. The error-correctionmethod will be described in detail later. For encryption, a public keycipher, such as the one shown in FIG. 18, is appended as a signature tothe serial number with a secret key that the software company has. Inthis case, since no one other than the software company has the secretkey and therefore cannot append a legitimate signature to a new serialnumber, this has an enormous effect in preventing illegal manufacturersfrom issuing a serial number. Since the public key cannot be deciphered,as previously described, the security is greatly enhanced. Disk piracycan thus be prevented even when the public key is recorded on the diskfor delivery.

The converging unit 914 in the optical disk barcode forming apparatus ofthe present embodiment will be described below in more detail.

As shown in FIG. 28(a), light emitted from the laser 912 enters theconverging unit 914 where the entering light is converted by acollimator 916 into a parallel beam of light which is then converged inonly one plane by a cylindrical lens 917, thus producing a stripe oflight. This light is limited by a mask 918, and is focused through aconverging lens 919 onto the reflective film 802 on the optical disk toremove the film in a stripe pattern. A stripe such as shown in FIG.28(b) is thus formed. In PE modulation, stripes are spaced apart atthree different intervals, 1T, 2T, and 3T. If this spacing is displaced,jitter occurs and the error rate rises. In the present invention, theclock generator 913 generates a modulating clock in synchronism with arotation pulse from the motor 915, and supplies this modulating clock tothe modulator 910 to ensure that each stripe 923 is recorded at acorrect position in accordance with the rotation of the motor 915, thatis, with the rotation of the disk 800. This has the effect of reducingjitter. Alternatively, a laser scanning means 950, such as shown in FIG.3(1), may be provided by which a continuous-wave laser is scanned in aradial direction to form a barcode.

(b) Next, a barcode recording method, etc., for forming a barcode usingthe above-described barcode recording apparatus, will be described withreference to FIG. 24 to 26.

FIG. 24 shows signals coded with RZ recording (polarity return-to-zerorecording) of the invention and trimming patterns formed correspondingto them. FIG. 25 shows signals coded with a conventional barcode formatand trimming patterns formed corresponding to them.

The present invention uses RZ recording, as shown in FIG. 24. In this RZrecording, one unit time is divided into a plurality of time slots, forexample, a first time slot 920a, a second time slot 921, a third timeslot 922, and so on. When data is "00", for example, a signal 924a of aduration shorter than the period of the time slot, that is, the period Tof a channel clock, is recorded in the first time slot 920a, as shown inpart (1) in FIG. 26. The pulse 924a whose duration is shorter than theperiod T of the recording clock is output between t=T1 and t=T2. In thiscase, using a rotation pulse from the rotation sensor 915a on the motor915, the clock signal generator 913 generates a modulation clock pulseas shown in part (1) of FIG. 24; by performing the recording insynchronism with the clock pulse, the effects of rotational variation ofthe motor can be eliminated. In this way, as shown in part (2) of FIG.24, a stripe 923a indicating "00" is recorded on the disk within arecording region 925a, the first of the four recording regions shown,and a circular barcode such as shown in part (1) of FIG. 27 is formed.

Next, when data is "01", a pulse 924b is recorded in the second timeslot 921b between t=T2 and t=T3, as shown in part (3) in FIG. 24. Inthis way, a stripe 923b is recorded on the disk within a recordingregion 926b, the second region from the left, as shown in part (4) ofFIG. 24.

Next, when recording data "10" and "11", these data are recorded in thethird time slot 922a and fourth time slot, respectively.

Here, for comparison purposes, NRZ recording (non-return-to-zerorecording) used for conventional barcode recording will be describedwith reference to FIG. 25.

In NZR recording, pulses 928a and 928b, each having a width equal to theperiod T of time slot 920a, are output, as shown in part (1) of FIG. 25.In RZ recording, the width of each pulse is 1/nT; on the other hand, inthe case of NZR recording, a pulse as wide as T is needed, andfurthermore, when T appears successively, a pulse of double or triplewidth, 2T or 3T, becomes necessary, as shown in part (3) of FIG. 25. Inthe case of laser trimming such as described in the present invention,changing the laser trimming width is practically difficult since itnecessitates changing settings, and therefore, NRZ is not suitable. Asshown in part (2) of FIG. 25, stripes 929a and 929b are respectivelyformed in the first and third recording regions 925a and 927a from theleft, and in the case of data "10", a stripe 929b of width 2T isrecorded in the second and third recording regions 929b and 927b fromthe left, as shown in part (4) of FIG. 25.

In the conventional NRZ recording, the pulse widths are 1T and 2T, asshown in parts (1) and (3) of FIG. 25; it is therefore apparent that NRZrecording is not suitable for the laser trimming of the presentinvention. According to the laser trimming of the present invention, abarcode is formed as shown in the experiment result shown in FIG. 8(a),but since trimming line width differs from disk to disk, it is difficultto precisely control the line width; when trimming the reflective filmon a disk, the trimming line width varies depending on variations inlaser output, thickness and material of the reflective film, and thermalconductivity and thickness of the substrate. Further, forming slots ofdifferent line widths on the same disk will result in an increasedcomplexity of the recording apparatus. For example, in the case of theNZR recording used for product barcode recording, as shown in parts (1)and (2) of FIG. 25, the trimming line width must be made to preciselycoincide with the period 1T of the clock signal, or 2T or 3T, that is,with nT. It is particularly difficult to record various line widths suchas 2T and 3T by varying the line width for each bar (each stripe). Sincethe conventional product barcode format is an NRZ format, if this formatis applied to the laser-recorded barcode of the present invention, thefabrication yield will decrease because it is difficult to preciselyrecord varying line widths such as 2T and 2T on the same disk;furthermore, stable recording cannot be done since the laser trimmingwidth varies. This makes demodulation difficult. Using RZ recording, thepresent invention has the effect of achieving stable digital recordingeven if the laser trimming width varies. Further,. the invention offersthe effect of simplifying the construction of the recording apparatussince RZ recording requires only one kind of line width and the laserpower therefore need not be modulated.

As described, by employing the above RZ recording for optical diskbarcode recording according to the invention, there is offered theeffect of ensuring stable digital recording.

An example of the phase-encoding (PE) modulation of RZ recording will bedescribed with reference to FIG. 26.

FIG. 26 shows signals and an arrangement of stripes when the RZrecording shown in FIG. 24 is PE-modulated. As shown, data "0" isrecorded in the left-hand time slot 920a of the two time slots 920a and921a; on the other hand, data "1" is recorded in the right-hand timeslot 921a, as shown in part (3) of FIG. 26. On the disk, data "0" isrecorded as a stripe 923a in the left-hand recording region 925a anddata "1" as a stripe 923b in the right-hand recording region 926b, asshown in parts (2) and (4) of FIG. 26, respectively. Thus, fordata"010", a pulse 924c is output in the left-hand time slot for "0", apulse 924d is output in the right-hand time slot for "1", and a pulse924e is output in the left-hand time slot for "0", as shown in part (5)of FIG. 26; on the disk, the first stripe is formed in the left-handposition, the second stripe in the right-hand position, and the thirdstripe in the left-hand position, by laser trimming. FIG. 26(5) showssignals modulated with data "010". As can be seen, a signal is alwaysavailable for every channel bit. That is, since the signal density isconstant, the DC component does not vary. Since the DC component doesnot vary, PE modulation is resistant to variation in low-frequencycomponents even if a pulse edge is detected during playback. This hasthe effect of simplifying playback demodulator circuitry of the diskplayback apparatus. Furthermore, since one signal 923 is alwaysavailable for every channel clock 2T, this has the effect of being ableto reproduce a synchronization clock for a channel clock without using aPLL.

A circular barcode, such as shown in FIG. 27(1), is thus formed on thedisk. When data "01000", shown in part FIG. 27(4), is recorded, in thePE-RZ modulation of the invention a barcode 923a having the same patternas the recorded signal shown in part (3) is recorded as shown in part(2). When this barcode is played back by an optical pickup, a signalwaveform, such as shown in part (5) REPRODUCED SIGNAL, is output withportions thereof dropped corresponding to missing portions of apit-modulated signal where no reflection signals are obtained due toremoval of the reflective film, as explained with reference to part FIG.5(6). By passing this reproduced signal through the second-order orthird-order LPF filter 934 shown in FIG. 35(a), the filtered signalwaveform shown in FIG. 27(6) is obtained. By slicing this signal by alevel slicer, reproduced data "01000" of part (7) is demodulated.

(C) We will next describe features of the optical disk format with abarcode formed in the above manner, tracking control methods, androtational speed control methods that can be used when playing back theoptical disk.

(a) We will first describe the features of the optical disk format witha barcode formed according to the present embodiment, while dealing withan example of a condition that permits tracking control during playback(this condition is also referred to as the tracking ON condition). Aplayback operation using tracking control is shown in FIG. 40, and itsdetails will be given later.

In the case of a DVD disk in the present embodiment, all data arerecorded in pits with CLV, as shown in FIG. 30. Stripes 923 (forming abarcode) are recorded with CAV. CLV recording means recording withconstant linear velocity, while CAV recording means recording withconstant angular velocity.

In the present invention, the stripes 923 are recorded with CAV,superimposed on a pre-pit signal in a lead-in data area holding anaddress which is recorded with CLV. That is, the data is overwrittenwith the stripes. In the present invention, the pre-pit signal area mapsinto all the data areas where pits are formed. The prescribed region ofthe pre-pit signal area, as mentioned in the present invention,corresponds to an inner portion of the optical disk; this region is alsocalled a post-cutting area (PCA). In this PCA area, the barcode isrecorded with CAV, superimposed on pre-bit signals. In this way, the CLVdata is recorded with a pit pattern from the master disk, while the CAVdata is recorded with laser-removed portions of the reflective film.Since the barcode data is written in overwriting fashion, pits arerecorded between the barcode stripes 1T, 2T, and 3T. Using this pitinformation, optical head tracking is accomplished, and Tmax or Tmin ofthe pit information can be detected; therefore, motor rotational speedis controlled by detecting this signal. To detect Tmin, the relationbetween the trimming width t of stripe 923a and the pit clock T (pit)should be t>14T (pit), as shown in FIG. 30, to achieve the above effect.If t is shorter than 14T, the pulse width of the signal from the stripe923a becomes equal to the pulse width of the pit signal, anddiscrimination between them is not possible, so that the signal from thestripe 923a cannot be demodulated. To enable pit address information tobe read at the same radius position as the stripes, an address area 944is provided longer than a unit of one address of pit information, asshown in FIG. 32; address information can thus be obtained, making itpossible to jump to the desired track. Furthermore, the ratio of thestripe area to the non-stripe area, that is, the duty ratio, is madeless than 50%, i.e., T(S)<T(NS); since the effective reflectivitydecreases only by 6 dB, this has the effect of ensuring stable focusingof the optical head.

Next, we will describe an example of a condition in which trackingcontrol cannot be applied during playback (this condition is alsoreferred to as the tracking OFF condition).

Since the stripes 923 are written over pits, interrupting pit signalsand preventing correct playback of the pit data, tracking control maynot be possible on some players. In such players, the strips 923, whichare CAV data, can be read by the optical pickup by applying rotationalcontrol using a rotational pulse from a Hall element, etc. in the motor17.

FIG. 31 shows a flowchart illustrating a procedure for operations in aplayback apparatus when pit data in the optical tracks in the stripearea cannot be correctly played back.

In FIG. 31, when a disk is inserted in step 930a, the optical head ismoved by a prescribed distance to the inner portion in step 930b. Theoptical head is thus positioned on the area where the stripes 923 ofFIG. 30 are recorded.

Here, it is not possible to correctly playback data from all the pitsrecorded in the stripe area 923. In this case, therefore, usual rotationphase control cannot be applied for the playback of the pit datarecorded with CLV.

In step 930c, rotational speed control is applied by using a rotationalsensor of a Hall element in the motor or by measuring the T(max) orT(min) or frequency of a pit signal. If it is determined in step 930ithat there are no stripes, the process jumps to step 930f. If there arestripes, the barcode is played back in step 930d, and when playback ofthe barcode is completed in step 930e, the optical head is moved in step930f to an outer area where no stripes are recorded. In this area, sinceno stripes are recorded, the pits are played back correctly and accuratefocus and tracking servo are achieved. Since the pit signal can beplayed back, usual rotation phase control can be performed to rotate thedisk with CLV. As a result, in step 930h, the pit signal is played backcorrectly.

By switching between the two rotation control modes, i.e., therotational speed control and the rotation phase control by pit signals,the effect is obtained that two different kinds of data, barcode stripedata and pit-recorded data, can be played back. Since the stripes arerecorded in the innermost area, switching means measures the radiusposition of the optical head from the optical head stopper or from theaddress of a pit signal, and based on the result of the measurement,correctly performs switching between the two rotation control modes.

(b) Referring next to FIGS. 41 and 42, we will describe two controlmethods for controlling the rotational speed when playing back thebarcode according to the present embodiment.

FIG. 41 shows the first rotational speed control method whereinrotational speed control is applied by detecting Tmax of a bit signal(Tmax means measuring time for a pit having the largest pit length ofvarious pit lengths).

A signal from the optical head is first subjected to waveshaping, andthen the pulse spacing of the pit signal is measured by an edge-spacingmeasuring means 953. A t0 reference value generating means 956 generatesreference value information t0 whose pulse width is larger than thepulse width 14T of the sync signal but smaller than the pulse width t ofthe barcode signal. This reference value information t0 and the pulsewidth TR of the reproduced signal are compared in a comparing means 954;only when TR is smaller than the reference value t0 and larger than Tmaxheld in a memory means 955, TR is supplied to the memory means 955 whereTR is set as Tmax. By reference to this Tmax, a controller 957 controlsa motor drive circuit 958, achieving motor rotational speed controlbased on Tmax. In the case of the present invention, numerous pulses atcycles of 3 to 10 μs are generated by barcode stripes, as shown in FIG.9(a). In the case of a DVD, the sync pulse width is 14T, that is, 1.82μm. On the other hand, the barcode stripe width is 15 μm. In Tmax-basedcontrol, the barcode pulse longer than the pulse width 14T of the synchpulse will be erroneously judged and detected as Tmax. Therefore, byremoving barcode signals larger than the reference value t0 bycomparison with the reference value t0, as shown in FIG. 41, it becomespossible to perform rotational speed control for normal rotational speedduring the playback of the barcode stripe area.

Next, the second rotational speed control method will be described withreference to FIG. 42. This method performs rotational speed control bydetecting Tmin (Tmin means measuring time for a pit having the smallestpit length of various pit lengths).

In the Tmin-based control shown in FIG. 42, the pulse information TRfrom the edge-spacing detecting means 953 is compared in a comparingmeans 954a with Tmin held in a memory means 955a; if TR<Tmin, a strobepulse occurs and the Tmin in the memory is replaced by TR.

In this case, the barcode pulse width t is 3 to 10 μm, as noted above,while Tmin is 0.5 to 0.8 μm. As a result, if the barcode area is playedback, the condition TR<Tmin is not satisfied since the barcode pulsewidth t is always greater than Tmin. That is, there is no possibility oferroneously judging a barcode pulse as Tmin. Therefore, when theTmin-based rotational speed control is combined with a barcode readingmeans 959, the effect is that rotational speed control based on Tmin canbe applied more stably while playing back the barcode, compared to theTmax-based method. Further, an oscillator clock 956 creates a referenceclock for demodulation in the barcode reading means 959, while detectingthe edge spacing; this has the effect of being able to demodulate thebarcode in synchronism with rotation.

(D) Next, a series of optical disk reproduction operations (playbackoperations) using the above control methods, etc. will be described.

Referring first to FIGS. 31 and 43, a first playback method will bedescribed in conjunction with a method for switching between rotationphase control mode and rotational speed control mode by a mode switch963. Then, a second and a third playback method for playing back theoptical disk of the present embodiment will be described with referenceto FIGS. 38, 40, etc. The first and second playback methods hereinafterdescribed are each concerned with a case where tracking control cannotbe performed, while the third playback method is concerned with a casewhere tracking control can be performed.

At the same time that the optical head is moved to the inner portion ofthe disk in steps 930b and 930c in FIG. 31, the mode switch 963 shown inFIG. 43 is switched to A. Alternatively, the mode switch 963 may beswitched to A when it is detected by a pickup (PU) position sensor 962,etc. that the optical head being moved by a moving means 964 has reachedthe inner portion of the disk.

Next, an operation when the rotational speed control mode (step 930c inFIG. 31) is entered will be described with reference to FIG. 43.

μmotor rotation frequency, fm, from a motor 969 and a frequency, f2, ofa second oscillator 968 are compared in a second frequency comparator967, and a difference signal is fed to the motor drive circuit 958 tocontrol the motor 969, thus achieving rotational speed control. In thiscase, since the disk is rotating with CAV, the barcode stripe can beplayed back.

When the barcode playback is completed in step 930e in FIG. 31, the headis moved to an outer area by the moving means 964, and at the same time,by a signal from the PU position sensor 962, etc., the mode switch 963is switched to B for rotation phase control mode.

In the rotation phase control mode, PLL control is applied to the pitsignal from the optical head by a clock extracting means 960. Thefrequency f1 of a first oscillator 966 and the frequency fS of areproduced synchronization signal are compared in a first frequencycomparator 965, and a difference signal is fed to the motor drivecircuit 958. The rotation phase control mode is thus entered. Because ofPLL phase control by the pit signal, data synchronized to thesynchronization signal of f1 is played back. If the optical head weremoved to the barcode stripe area by rotation phase control, withoutswitching between rotational phase control for the motor and rotationalspeed control for the motor, phase control could not be performedbecause of the presence of the stripes, and trouble would occur, suchas, the motor running out of control or stopping, an error conditionoccurring, etc. Therefore, as shown in FIG. 43, switching to theappropriate control mode not only ensures stable playback of the barcodebut has the effect of avoiding troubles relating to motor rotation.

The second method for playing back the optical disk of the presentembodiment will be described with reference to FIG. 38 which shows aflowchart illustrating the operation.

The second playback method is an improved version of the first playbackmethod.

More specifically, the first playback method is a method for playingback an optical disk on which a stripe presence/absence identifier 937is not defined. Since tracking is not applied in the stripe area on anoptical disk of this type, it takes time to distinguish between a stripepattern legally formed on the disk and an irregular pattern caused byscratches on the disk surface. Therefore, regardless of whether thestripes are recorded or not, the playback procedure has to perform astripe reading operation first, to check the presence or absence ofstripes or whether the stripes are recorded in the inner portion of theoptical disk. This may cause a problem in that an extra time is requiredbefore the data can be actually played back. The second playback methodimproves on this point.

First, as shown in FIG. 38, when an optical disk is inserted, controldata is played back in step 940a. Usually, physical feature informationand attribute information of the optical disk are recorded as controldata in a control data area. The physical feature information includes,for example, information indicating that the optical disk is alaminated-type disk of a two-layer, single-sided structure.

In the present invention, as shown in FIG. 30, the control data recordedin the control data area 936 of the optical disk contains a PCA stripepresence/absence identifier 937 recorded as a pit signal. Therefore, theoptical bead is first moved, in step 940n, to an outer area where thecontrol data is recorded. And then the optical head moves inwardlyjumping across a plurality of tracks until reaching the control dataarea 436. And then in step 940a, the control data is played back. It canthus be checked whether the stripes are recorded or not. If, in step940b, the stripe presence/absence identifier is 0, the process proceedsto step 940f to initiate rotation phase control for normal playback withCLV. On the other hand, if, in step 940b, the presence/absenceidentifier 937 is 1, then the process proceeds to step 940h to check thepresence or absence of a reverse-side record identifier 948 whichindicates that the stripes are recorded on the side opposite from theside being played back, that is, on the reverse side. If the stripes arerecorded on the reverse side, the process proceeds to step 940i to playback the recording surface on the reverse side of the optical disk. Ifthe reverse side cannot be automatically played back, an indication isoutput for display, to urge the user to turn over the disk. If it isdetermined in step 940h that the stripes are recorded on the side beingplayed back, the process proceeds to step 940c, where the head is movedto the stripe area 923 in the inner portion of the disk, and in step940d, the control mode is switched to rotational speed control to playback the stripes 923 with CAV rotation. If the playback is completed instep 940e, then in step 940f the control mode is switched back torotation phase control for CLV playback and the optical head is moved tothe outer portion of the disk to play back pit signal data.

Since the stripe presence/absence identifier 937 is recorded in the pitarea holding the control data, etc., as described above, the secondmethod has the effect of being able to play back the stripes morereliably and more quickly compared to the first playback methoddescribed with reference to FIG. 31.

When the PCA area is with tracking OFF, level of the noise signal whichis generated by the pits drops. PCA signal level remains unchanged iftracking is set OFF. Therefore, in the filtered waveform shown in FIG.35(b), the pit signal drops, making it easier to distinguish between thePCA signal and the pit signal. This has the effect of simplifying thecircuitry and reducing the error rate.

Furthermore, the provision of the stripe reverse-side record identifier948 makes it possible to identify that the stripes are recorded on thereverse side of the disk; the effect is that the barcode stripes can beplayed back reliably in the case of a double-sided DVD optical disk.According to the present invention, since the stripes are recordedpenetrating through the reflective films on both sides of a disk, thestripe pattern can also be read from the reverse side of the disk. Thestripes can be played back from the reverse side of the disk by checkingthe stripe reverse-side identifier 948 and by playing back the code inthe reverse direction when reading the stripes. The present inventionuses a bit string "01000110" as the synchronization code, as shown inFIG. 34(a). When played back from the reverse side, the synchronizationcode is played back as "01100010", from which it can be detected thatthe barcode is being played back from the reverse side. In this case, bydemodulating the code in reverse direction in the demodulator 942 in theplayback apparatus of FIG. 15, the barcode recorded in penetratingfashion can be correctly played back even if played back from thereverse side of a double-sided disk. The playback apparatus of FIG. 15will be described in more detail later.

Further, if, as shown in FIG. 30, a 300-μm wide guard-band area 999,where only address information is recorded but no other data isrecorded, is provided between the PCA area 998 and the control data area936, access to the control data can be made more stable.

The guard-band area 999 will be described in more detail below.

When the optical head accesses the control data from the outer portionof the disk, the optical head moves inwardly jumping across a pluralityof tracks until reaching the control data area 936. In some cases, theoptical head may be moved past the destination control data area 936,landing at a portion further inward of the control data area. At thistime, if the PCA area 998 exists directly adjacent to the innercircumference of the control data area, the optical head will lose itsown position since an address cannot be played back in the PCA area 998.It, then, becomes impossible to control the optical head.

Accordingly, when the guard-band area with a width, for example, 300 μm,greater than one jump width of the optical head, is provided in theabove-noted portion, if the optical head is moved past the control dataarea 936 the optical head will always land within the guard-band area.Then, by reading an address in the guard-band area, the optical headknows its own position and can thus be repositioned on the destinationcontrol data area. In this way, the optical head can be controlled morereliably and more quickly.

Further, as shown in FIG. 30, the control data also contains anadditional stripe data presence/absence identifier and a striperecording capacity. That is, after recording first stripes on an opticaldisk, additional stripes can be recorded in an empty, unrecorded portionof the area. The first recorded stripes will be referred to as the firstset of stripes, and the additionally recorded stripes as the second setof stripes. With this configuration, when the first set of stripes 923is already recorded by trimming, as shown in FIG. 30, the capacity ofthe available space for trimming the second set of stripes 938 can becalculated. Accordingly, when the recording apparatus of FIG. 23performs trimming to record the second set of stripes, the control dataprovides an indication of how much space is available for additionalrecording; this prevents the possibility of destroying the first set ofstripes by recording more than 360° over the area. Furthermore, as shownin FIG. 30, a gap 949 longer than one pit-signal frame length isprovided between the first set of stripes 923 and the second set ofstripes 938; this serves to prevent the previously recorded trimmingdata from being destroyed.

Moreover, as shown in FIG. 34(b) to be described later, a trimming countidentifier 947 is recorded in a synchronization code area. Thisidentifier is used to distinguish between the first set of stripes andthe second set of stripes. Without this identifier, discriminationbetween the first set of stripes 923 and the second set of stripes 938in FIG. 30 would become impossible.

Finally, the third playback method will be described with reference toFIG. 40.

When the duty ratio of the stripe on the optical disk, that is, its arearatio, is low, almost correct tracking can be maintained in the stripearea, as shown in FIG. 32. Therefore, the address information in theaddress area 944 at the same radius position of the disk can be playedback. This has the effect of quickening the disk rise time after diskinsertion since the address can be played back while playing back thestripes without changing the optical head position.

In this case, the address area, an area where no stripes are recorded,should be formed continuously along a length longer than one frame inthe same radium portion of the disk.

The operation steps for this method will be described with reference toFIG. 40.

When a disk is inserted, the optical head is moved to the innercircumferential portion in step 947a. If no tracking is achieved in step947n, the tracking mode is switched from phase control to push-pull modein step 947p. In step 947b, rotational speed control (CAV control) isperformed to play back address information. If an address cannot beplayed back in step 947c, the process proceeds to step 947i to move theoptical head inward to play back the PCA stripes. If an address can beplayed back from an empty portion of the PCA area (a portion notoverwritten), the process proceeds to step 947e where, based on theaddress, the optical head is moved in a radial direction to the addressarea where stripes are recorded. In step 947q, the presence or absenceof PCA stripes is checked. If it is judged that there are no PCAstripes, the process proceeds to step 947r to try to read a PCA flag inthe control data. Then, in step 947s, the presence or absence of the PCAflag is checked. If the presence of the PCA flag is detected, theprocess returns to step 947c; otherwise, the process jumps to step 947m.

On the other hand, if it is judged in step 947q that there are PCAstripes, the process proceeds to step 947f to play back the PCA stripes.When the playback is completed in step 947g, then the mode is switchedto rotation phase control and the optical head is moved to the outerarea to play back a pit signal. In step 947t, the PCA flag in thecontrol data is read; if there is no PCA flag, an error message isissued in step 947k, and the process returns to 947m to continue theprocess.

(E) Next, manufacturing techniques for implementing the optical diskbarcode forming method of the invention will be described in furtherdetail. A barcode playback apparatus will also be described briefly.

(a) First, manufacturing techniques for implementing the barcoderecording method will be described.

In the case of the barcode recording method previously explained withreference to FIG. 28, the minimum emitting-pulse spacing is lt;therefore, a laser with a pulse repetition period of fC=1/f_(L) isrequired, where f_(L) is the frequency of the laser. In this case, thenumber, f_(L) /2, of barcode bars can be recorded per second. However,if a beam deflector 931 is used, as shown in FIG. 29, a minimumemitting-pulse spacing of 2t is allowed, so that the pulse repetitionperiod is f_(L) =1/2t, which means that the laser frequency can bereduced by a factor of 2. This also means that, when a laser of the samefrequency is used, the number of barcode bars that can be recorded persecond can be doubled to fL by using the beam deflector 931. This hasthe effect of reducing the productive tact (processing tact) by a factorof 2.

The operation of a double-efficiency apparatus (referred to as "switchrecordings") using the beam deflector 931 will be described below withreference to FIG. 29, focusing on differences from the configuration ofFIG. 28.

The beam deflector 931, formed from an acousto-optical modulator or thelike, is supplied with a deflection signal for switching the beambetween a main beam 945 and a sub-beam 946; when the deflection signalis ON, the beam is switched to the sub-beam 946 which is passed througha sub-slit 932b and forms a sub-stripe 934. More specifically, for data"0" a normal stripe 933 is formed; only when recording data "1" is thedeflection signal set to ON, as shown in FIG. 29(b), in response towhich the beam deflector 931 switches the beam to the sub-beam 946 torecord a stripe at the position of the sub-stripe 934. In this manner,stripes 933a and 933b, each for "0", and a stripe 934a for "1", as shownin part (b), are formed on the disk. In this configuration, since alaser pulse need only be produced at intervals of 2t, a laser with afrequency half that required in the configuration of FIG. 28 can beused. In other words, when a laser of the same frequency is used, sincethe stripes can be formed at twice the clock frequency, this has theeffect of increasing the productivity by a factor of 2, as alreadydescribed.

Next, referring to the data structure of the synchronization code shownin FIG. 34, a format suitable for the switch recording explained withreference to FIG. 29 will be described below. The synchronization codedata structure also constitutes a technique for improving productivity.

As shown in FIG. 34(a), a fixed pattern of "01000110" is used here.Conventionally, a bit string consisting of the same number of 0s and 1s,such as "01000111", is used, but the present invention deliberatelyavoids this and uses the illustrated data structure for the reasonexplained below.

First, to achieve the switch recording of FIG. 29, provisions must bemade so that two or more pulses will not occur within one time slot,that is, within 1T interval. Switch recording is possible in the dataarea because data is recorded there with a PE-RZ code, as shown in FIG.33(a). However, in the case of the synchronization code of FIG. 34(a),since irregular channel bits are arranged, with the usual method twopulses may occur within 1T in which case the switch recording of theinvention is not possible. To address this problem, the inventionemploys, for example, the bit pattern "01000110" as shown in FIG. 37.With this bit pattern, in T1 a pulse occurs for the "1" on the right, inT2 no pulses occur, in T3 a pulse occurs for the "1" on the right, andin T4 a pulse occurs for the "1" on the left; in this way, two or morepulses cannot occur within one time slot. Thus, the synchronization codestructure of the invention has the effect of achieving switch recording,increasing the production rate by a factor of 2.

(b) Next, referring to FIG. 15, a brief description will be given of aplayback apparatus for playing back the barcode recorded on an opticaldisk by the above method. The description will also touch onproductivity increases.

FIG. 15 is a block diagram of the playback apparatus already describedin (I).

In the first-half part (I), the apparatus has been described as anapparatus for reading the position of a marking formed on the reflectivefilm of an optical disk, but hereinafter, the apparatus of FIG. 15 willbe described as a barcode reading apparatus, that is, a playbackapparatus.

An explanation will be given again referring to FIG. 15, this timefocusing on the demodulation operation. First, high-frequency componentsgenerated by pits are removed by a low-pass filter (LPF filter) 94 froma stripe signal output.

In the case of a DVD, there is a possibility that a maximum 14T signalmay be played back, where T=0.13 μm. In this case, it has been confirmedby experiment, a stripe signal and a high-frequency component generatedby a pit can be separated by using the second-order or third-orderChevihov low-pass filter shown in FIG. 35(a). That is, the use of asecond- or higher-order LPF has the effect of being able to separate apit signal and a barcode signal, thus ensuring stable playback of abarcode. FIG. 35(b) shows the simulation waveform which is generatedwhen the signal of the maximum 14T pit length is recorded continuously.

In this way, by using the second- or higher-order LPF 943, the stripeplayback signal can be output after substantially removing the pitplayback signal; this ensures reliable demodulation of stripe signals.However, if the width of a stripe signal thus demodulated (the stripesignal width shown as 15 μm in FIG. 36(b)) is smaller than the samplinginterval width tm (see FIG. 36(c)) of a microcomputer, the stripe signalmay not be measured accurately. For example, of the stripe signals shownin FIG. 36(b), the stripe signal on the left is located inside of themicrocomputer sampling interval width, and therefore, is not detected.To avoid this, a stripe signal obtained by reading a stripe iswaveshaped using a flip-flop circuit so that the signal width becomesgreater than the microcomputer sampling interval width tm, as shown inFIG. 36(d). FIG. 36(d) shows a waveform after the stripe signal widthwas increased to a width Bw. The waveshaped signal is then detected withsampling pulses (see FIG. 36(c)) from the microcomputer. This ensuresaccurate measurement of the stripe signal.

Referring back to FIG. 15, a further description will be given. Digitaldata is demodulated by the PE-RZ demodulator 942 in the above manner.The data is then fed to an ECC decoder 928 for error correction. Thatis, deinterleaving is performed in a deinterleaver 928a, andReed-Solomon code computation is performed in an RS decoder 928b forerror correction.

A brief description will now be given in relation to productive tact.

FIG. 33(a) shows the data structure after the barcode is ECC encodedaccording to the present embodiment. FIG. 33(b) shows the data structureafter ECC encoding when n=1 according to the present embodiment. FIG.33(c) shows an ECC error-correction capability according to the presentembodiment.

In the present invention, the interleaving and Reed-Solomonerror-correction coding shown in the data structure of FIG. 33(a) areperformed using the ECC encoder 927 shown in FIG. 1 when recordingstripes on an optical disk. With this error-correction method, a readerror occurs in only one disk out of 10⁷ =10 million optical disks underthe condition of that Byte error rate of 10⁻⁴ occurs, as shown in FIG.33(c). In this data structure, to reduce the code data length the samesync code is assigned to four rows, reducing the number of sync codes bya factor of 4 and thus increasing efficiency. With further reference toFIG. 33, the scalability of the data structure will be described. In thepresent invention, the recording capacity can be varied freely, forexample, within a range of 12 B (12 Byte) to 188 B in increments of 16B, as shown in the example of FIG. 34(c). That is, n can be changedwithin a range of n=1 to n=12, as shown in FIG. 33(c).

As shown in FIG. 33(b) and FIG. 14(a), for example, in the datastructure when n=1, there are only four data rows 951a, 951b, 951c, and951d, followed by ECC rows 952a, 952b, 952c, and 952d. FIG. 14(a) is adiagram showing FIG. 33(b) in further detail. The data row 951constitutes EDC of 4B. FIG. 14(b) shows this in an equivalent form.Error-correction encoding computation is performed, assuming that datarows from 951e to 951z all contain 0s. Mathematical equations for EDCand ECC computations are shown in FIGS. 14(c) and 14(d), respectively.In this way, the data is ECC-encoded by the ECC encoder 927 in therecording apparatus of FIG. 1 and recorded as a barcode on the disk.When n=1, data of 12 B is recorded over an angle of 51 degrees on thedisk. Likewise, when n=2, data of 18 B can be recorded; when n=12, dataof 271 B can be recorded over an angle of 336 degrees on the disk. Inthe present invention, by encoding and decoding the data using the EDCand ECC computation equations shown in FIGS. 14(c) and 14(d), when thedata amount is smaller than 188 B, the computation is performed assumingall remaining bits are 0s, so that the data is stored with a smallrecording capacity. This serves to shorten the productive tact. Whenperforming laser trimming, as in the present invention, theabove-described scalability has a significant meaning. Morespecifically, when performing laser trimming at a factory, it isimportant to shorten the productive tact. With a slow-speed apparatuswhich trims one stripe at a time, it will take more than 10 seconds torecord a few thousand stripes to the full capacity. The time requiredfor disk production is 4 seconds per disk; if full-capacity recordinghas to be done, the productive tact increases. On the other hand, forthe moment, disk ID number will be a main application area of thepresent invention; in this application, the PCA area capacity can be aslow as 10 B. If 271 B are recorded when only 10 B need to be written,the laser processing time will increase by a factor of 6, leading to aproduction cost increase. The scalability method of the presentinvention achieves reductions in production cost and time.

In the playback apparatus shown in FIG. 15, when n=1 as in FIG. 33(b),for example, the ECC decoder 928 performs the EDC and ECCerror-correction computations shown in FIGS. 14(c) and 14(d), assumingthat the data rows 951e to 951z all contain 0s, as shown in FIG. 14(b);the effect of this is that data of 12 to 271 B can be corrected forerrors by using the same program. In this case, the number of programsteps decreases, permitting the use of a small-capacity ROM in themicrocomputer.

Furthermore, the pulse width reproduced from each stripe width is madeless than 1/2 of one pulse period, as shown in FIG. 36. Since there arethree difference pulse spacings, 1T, 2T, and 3T, the ratio of the sum ofall the stripe areas in one track to the total area of the track is lessthan 1/3. With this arrangement, in the case of a disk of standardreflectivity of 70% the reflectivity of the stripe area is 2/3 of that,i.e., about 50%. Since this value is enough for focus control, the PCAarea can be played back on a conventional ROM disk player.

(F) Next, an example of the above-described barcode encryption(including digital signature) will be described with reference todrawings, followed by a description of another application example ofthe barcode.

(a) First, the barcode encryption process and playback process will bedescribed by way of example with reference to FIG. 45.

As shown in FIG. 45, an ID number 4504 unique to each individual opticaldisk is generated by an ID generator 4502. At the same time, an IDsignature section 4503 applies a digital signature to the ID number byusing a specific secret key corresponding to a specific public key, andthe thus applied digital signature 4505 and its associated ID number4504 are sent together as a series of data to a press factory 4501. Thisdigital signature is applied to the ID number encrypted in an encryptionencoder 4508 using a secret key of a public key encryption function. Thepublic key corresponding to this secret key is sent to the press factory4501. At the press factory 4501, the ID number and its correspondingdigital signature 4505 are recorded as a barcode in the PCA area of anoptical disk 4506 by using a PCA writer 4507. The public key isprerecorded on the master disk, that is, in a pit portion of the disk.When the thus manufactured optical disk 4506 is loaded into a playbackapparatus (player) 4509, the public key is read from the pit portion,and the ID number and the digital signature appended to it are read fromthe PCA area and decrypted with the public key. The result of thedecryption is passed to a verification section 4511; if the digitalsignature data is found legitimate as the result of the verification,the playback operation of the optical disk is allowed to continue. Ifthe digital signature data is found illegitimate as the result of theverification, the operation is stopped. Here, if the digital signaturedata is recorded in the PCA area together with the plaintext of the ID,the result of the decryption is checked against the plaintext of the IDto see if they match. If the digital signature data only is recorded inthe PCA area, an error check is performed for verification. When thedata is encrypted with public key cipher, as described above, only thesoftware manufacturer that has the secret key can issue a new ID number.Accordingly, if pirated disks were made, the encrypted ID of the samenumber would be recorded in the PCA area of every disk; therefore, theuse of such pirated disks would be greatly limited. The reason is that,in such cases, the illegal use of the software having the same numbercan be prevented by applying network protection. Needless to say, theabove method described with reference to FIG. 45 can also be used in theInternet.

(b) Another application example of the barcode will be described withreference to FIG. 46 as another mode of embodiment.

This mode of embodiment is concerned with an example in which anencryption key to be used during communication is recorded as theabove-described barcode in the PCA area.

As shown in FIG. 46, a press factory 4601 keeps each ID number and itscorresponding encryption key, a public key of a public key encryptionfunction, in the form of a table 4602. At the press factory 4601, an IDnumber and its corresponding public key are recorded in the PCA area4605 of an optical disk 4604 by using a PCA writer 4603.

Next, we will describe how the user who purchased the thus completedoptical disk 4604 can play it back on his player. Consider, for example,a case in which he desires to watch movie software recorded on theoptical disk. Before the user can play back the movie contained on theoptical disk 4604, he has to arrange for payment to a system managementcenter 4610 and have a password issued to enable playback.

First, the user sets the optical disk 4604. With communication softwarerun on a personal computer 4606, the PCA area, etc. are played back andthe public key is read out. When the user enters his credit card numberand personal code number, an encryption encoder 4607 encrypts theentered data with the public key, and the encrypted data is transmittedto the system management center 4610 by using the communications channel4620. At the system management center 4610, a communication section 4611reads the ID number in plaintext from the received data, and decryptsthe received data by retrieving a secret key corresponding to the IDnumber from an encryption key table 4612. That is, the system managementcenter 4610 keeps the encryption key table 4612 containing mappinginformation for each ID number and a secret key corresponding to thepublic key. Based on the user's credit card number and personal codenumber retrieved from the decrypted data, the system management center4610 charges the user, and at the same times, issues a password to theuser. This password corresponds to the disk ID and user-specified movieor computer software contained on the disk 4604. Using the password thusissued, the user can play back the desired movie or install the desiredcomputer software.

Since the public key can be prerecorded as a barcode on the opticaldisk, this mode of embodiment has the effect of saving time and labortaken in a previous system that required the system management center tosend the public key to the user separately. Furthermore, even if thecommunication key (public key) is delivered to a press factory where noparticular security measures are implemented, security can bemaintained. Furthermore, since a different public key is used for eachindividual disk, if security of one particular disk, that is, one user,is broken, the security of other users can be protected. Furthermore,using different public keys for different disks has the effect ofreducing the possibility of a third party placing an illegal order. Ifthe communication public key were recorded on the master disk, it wouldnot be possible to prevent a third party from placing an illegal order.In the example of FIG. 46, a public key is used as the communicationkey, but it will be appreciated that similar effects can be obtained ifa secret key is used. In this case, however, the security level is alittle lower than when a public key is used. Needless to say, the methoddescribed with reference to FIG. 46 can also be used in the Internet.

Referring to FIG. 22, we will now describe in detail a method ofdescrambling and decrypting data using a password via the networkdescribed with reference to FIG. 46. In the flowchart of FIG. 22, firstin step 901a the software on the disk checks the scramble identifier tosee if the identifier is ON. If the answer is NO, the process proceedsto step 901b; if the software is not. scrambled, the installation isallowed to continue. On the other hand, if the answer is YES, it ischecked in step 901b whether the software is scrambled or not; if YES, aconnection is made to the personal computer network in step 901c, whichis followed by step 901d where the user enters the user ID and softwareID. If, in step 901c, there is a drive ID, then in step 901f the driveID data is transmitted to the password issuing center. After confirmingpayment, in step 901g the password issuing center performs encryptioncomputation on the drive ID and software ID by using a sub secret key,and generates a password which is transmitted to the user. The processthen proceeds to step 901h. The personal computer at the user endcomputes the password by a sub public key and compares it with the driveID. If the result is OK, the process proceeds to step 901n where thesoftware scramble or encryption is unlocked.

Turning back to step 901e, if the answer is NO, then in step 901h it ischecked whether there is a disk ID. If there is a disk ID, then in step901i the disk ID data is transmitted to the password issuing center.After confirming payment, in step 901j the password issuing centerperforms encryption computation on the disk ID and software ID by usinga sub secret key, and generates a password which is transmitted to theuser. In step 901m, the personal computer at the user end computes thepassword by a sub public key and compares it with the drive ID. If theresult is OK, the process proceeds to step 901n where the softwarescramble is unlocked.

In this way, by communicating with the password issuing center via thenetwork by using a disk ID, the software scramble or encryption on thedisk can be unlocked. In the case of the disk ID of the presentinvention, since the ID varies from disk to disk, the password is alsodifferent; this has the effect of enhancing security. In FIG. 22,ciphertext communication is omitted, but by encrypting data using apublic key recorded in the PCA area, such as shown in FIG. 46, duringthe communication performed in steps 901i and 901j, data security duringcommunication can be further enhanced. This has the effect of ensuringsafe transmission of personal billing information via a communicationmeans such as the Internet where the security level is low.

We will finish here the descriptions of the first-half part (I) and thesecond-half part (II), and now proceed to a description of appertainingmatters relating to the process from optical disk manufacturing to theplayback operation of the player.

(A) A low reflectivity portion address table, which is a positioninformation list for the low reflectivity portion, will be explained.

(a) Laser markings are formed at random in the anti-piracy markformation process at the factory. No laser markings formed in thismanner can be identical in physical feature. In the next process step,the low reflectivity portion 584 formed on each disk is measured with aresolution of 0.13 μm in the case of a DVD, to construct a lowreflectivity portion address table 609 as shown in FIG. 13(a). Here,FIG. 13(a) is a diagram showing a low reflectivity portion addresstable, etc. for a legitimate CD manufactured in accordance with thepresent embodiment, and FIG. 13(b) is concerned with an illegallyduplicated CD. The low reflectivity portion address table 609 isencrypted using a one-direction function such as the one shown in FIG.18, and in the second reflective-layer forming step, a series of lowreflectivity portions 584c to 584e, where the reflective layer isremoved, is recorded in a barcode-like pattern on the innermost portionof the disk, as shown in FIG. 2. FIG. 18 is a flowchart illustrating adisk check procedure by the one-way function used for the encryption. Asshown in FIG. 13, the legitimate CD and the illegally duplicated CD havethe low reflectivity portion address tables 609 and 609x, respectively,which are substantially different from each other. One factor resultingin this difference is that laser markings identical in physical featurecannot be made, as earlier noted. Another factor is that the sectoraddress preassigned to the disk is different if the master disk isdifferent.

Referring now to FIG. 13, we will describe how the marking positioninformation differs between the legitimate disk and pirated disk. Thefigure shows an example in which the above two factors are combined. Inthe example shown, two markings are formed on one disk. In the case ofthe legitimate CD, the first marking of mark number 1 is located at the262nd clock position from the start point of the sector of logicaladdress A1, as shown in the address table 609. In the case of a DVD, oneclock is equivalent to 0.13 μm, and the measurement is made with thisaccuracy. On the other hand, in the case of the pirated CD, the firstmarking is located at the 81st clock position in the sector of addressA2, as shown in the address table 609x. By detecting this difference ofthe first marking position between the legitimate disk and pirated disk,the pirated disk can be distinguished. Likewise, the position of thesecond marking is also different. To make the position information matchthat of the legitimate disk, the reflective film at the 262nd positionin the sector of address A1 must be formed with an accuracy of one clockunit, i.e., 0.13 μm; otherwise, the pirated disk cannot be run.

In the example of FIG. 16, the legitimate disk and illegally duplicateddisk have low reflectivity portion address tables 609 and 609xrespectively, where values are different as shown in FIG. 17. In thecase of the legitimate disk, in the track following the mark 1 the startand end positions are m+14 and m+267, respectively, as shown in FIG.16(8), whereas in the case of the illegally duplicated disk these. arem+24 and m+277, respectively, as shown in FIG. 16(9). Therefore, thecorresponding values in the low reflectivity portion address tables 609and 609x are different, as shown in FIG. 17, thus making it possible todistinguish the duplicated disk. If an illegal manufacturer desires tomake a copy of the disk having the low reflectivity portion addresstable 609, they will have to perform a precise laser trimming operationwith the resolution of the reproduced clock signal as shown in FIG.16(8).

As shown in FIG. 20(5) showing the waveform of a PLL reproduced clocksignal out of reproduced optical signals, in the case of a DVD disk theperiod T of one reproduced clock pulse, when converted to a distance onthe disk, that is, one pulse spacing on the disk, is 0.13 μm.Accordingly, to make an illegal copy, the reflective film will have tobe removed with a submicron resolution of 0.1 μm. It is true that whenan optical head designed for an optical disk is used, a recording can bemade on a recording film such as a CD-R with a submicron resolution. Butin this case, the reproduced waveform will be as shown in FIG. 9(c), andthe distinct waveform 824 as shown in FIG. 9(a) cannot be obtainedunless the reflective film is removed.

(b) A first method of achieving mass production of pirated disks byremoving the reflective film may be by laser trimming using a highoutput laser such as a YAG laser. At the present state of technology,even the most highly accurate machining laser trimming can only achievea processing accuracy of a few microns. In the laser trimming forsemiconductor mask corrections, it is said that 1 μm is the limit of theprocessing accuracy. This means that it is difficult to achieve aprocessing accuracy of 0.1 μm at the mass production level.

(c) As a second method, X-ray exposure equipment for processingsemiconductor masks for VLSIs and ion beam processing equipment areknown at the present time as equipment that can achieve a processingaccuracy of the order of submicrons, but such equipment is veryexpensive and furthermore, it takes much time to process one piece ofdisk, and if each disk were processed using such equipment, the cost perdisk would be very high. At the present time, therefore, the cost wouldbecome higher than the retail price of most legitimate disks, so thatmaking pirated disks would not pay and meaningless.

(d) As described above, with the first method that involves lasertrimming, it is difficult to process with a submicron accuracy, andtherefore, it is difficult to mass produce pirated disks. On the otherhand, with the second method using the submicron processing technologysuch as X-ray exposure, the cost per disk is so high that making pirateddisks is meaningless from an economic point of view. Accordingly, makingillegal copies can be prevented until some day in the future whenlow-cost submicron processing technology for mass production becomespractical. Since practical implementation of such technology will bemany years into the future, production of pirated disks can beprevented. In the case of a two-layer disk with a low reflectivityportion formed on each layer as shown in FIG. 33, an illegallyduplicated disk cannot be manufactured unless the pits on top and bottomare aligned with good accuracy when laminating, and this enhances theeffectiveness in preventing piracy.

(B) Next, we will describe how the arrangement angle of the lowreflectivity portion on the disk can be specified.

In the present invention, sufficient effectiveness in piracy preventionis provided by the reflective layer level mechanism, that is, by the lowreflective marking alone. In this case, the prevention is effective evenif the master disk is a duplicate. However, the effectiveness can beenhanced by combining it with the piracy prevention technique at themaster disk level. If the arrangement angle of the low reflectivityportion on the disk is specified as shown in Table 532a and Table 609 inFIG. 13(a), an illegal manufacturer would have to accurately duplicateeven the arrangement angle of each pit on the master disk. This wouldincrease the cost of pirated disks and hence enhance the capability todeter piracy.

(C) A further description will be given of the operation of reading thenonreflective optical marking portion of the two-disk laminated opticaldisk, focusing on points that were not touched on in the foregoingdescription of the operating principle.

That is, as shown in FIG. 16, the start position address number, framenumber, and clock number can be measured accurately with a resolution of1T unit, that is, with a resolution of 0.13 μm in the case of the DVDstandard, by using a conventional player, thereby to accurately measurethe optical mark of the present invention. FIGS. 20 and 21 show theoptical mark address reading method of FIG. 16.

Explanation of signals (1), (2), (3), (4), and (5) in FIGS. 20 and 21will not be given here since the operating principle is the same as thatshown in FIG. 16.

The correspondence between FIG. 16, which illustrates the principle ofthe detection operation for detecting the position of a low reflectivityportion on a CD, and FIGS. 20 and 21, which are concerned with a DVD, isgiven below.

FIG. 16(5) corresponds to FIGS. 20(1) and 21(1). The reproduced clocksignal in FIG. 16(6) corresponds to that shown in FIGS. 20(5) and 21(5).Address 603 in FIG. 16(7) corresponds to that shown in FIGS. 20(2) and21(2).

Frame synch 604 in FIG. 16(7) corresponds to that shown in FIGS. 20(4)and 21(4). Starting clock number 605a in FIG. 16(8) corresponds toreproduced channel clock number in FIG. 20(6). Instead of the end clocknumber 606 in FIG. 16(7), in FIGS. 20(7) and 21(7) data is compressedusing a 6-bit marking length.

As illustrated, the detection operation is fundamentally the samebetween CD and DVD. A first difference is that a 1-bit mark layeridentifier 603a as shown in FIG. 20(7) is included for identifyingwhether the low reflectivity portion is of the one-layer type ortwo-layer type. The two-layer DVD structure provides a greateranti-piracy effect, as previously described. A second difference is thatsince the line recording density is nearly two times as high, 1T of thereproduced clock is as short as 0.13 μm, which increases the resolutionfor the detection of the position information and thus provides agreater anti-piracy effect.

Shown in FIG. 20 is the signal from the first layer in a two-layeroptical disk having two reflective layers. The signal (1) shows thecondition when the start position of an optical mark on the first layeris detected. FIG. 21 shows the condition of the signal from the secondlayer.

To read the second layer, a first/second layer switching section 827 inFIG. 15 sends a switching signal to a focus control section 828 whichthen controls a focus driving section 829 to switch the focus from thefirst layer to the second layer. From FIG. 20, it is found that the markis in address (n), and by counting the frame synchronizing signal (4)using a counter, it is found that the mark is in frame 4. From signal(5), the PLL reproduced clock number is found, and the optical markingposition data as shown by the signal (6) is obtained. Using thisposition data, the optical mark can be measured with a resolution of0.13 μm on a conventional consumer DVD player.

(D) Additional matters relating to the two-disk laminated optical diskwill be further described below.

FIG. 21 shows address position information pertaining to the opticalmarking formed on the second layer. Since laser light penetrates thefirst and second layers through the same hole, as shown in the processstep (6) in FIG. 7, the nonreflective portion 815 formed on the firstreflective layer 802 and the nonreflective portion 826 formed on thesecond reflective layer 825 are identical in shape. This is depicted inthe perspective view of FIG. 47. In the present invention, after thetransparent substrate 801 and the second substrate 803 are laminatedtogether, laser light is applied penetrating through to the second layerto form an identical mark thereon. In this case, since coordinatearrangements of pits are different between the first and second layers,and since the positional relationship between the first and secondlayers is random when laminating them together, the pit positions wherethe mark is formed are different between the first and second layers,and entirely different position information is obtained from each layer.These two kinds of position information are encrypted to produce ananti-piracy disk. If it is attempted to duplicate this disk illegally,the optical marks on the two layers would have to be aligned with aresolution of about 0.13 μm. As previously described, at the presentstate of technology it is not possible to duplicate the disk by aligningthe optical marks with the pits with an accuracy of 0.13 μm, that is,with an accuracy of the order of 0.1 μm, but there is a possibility thatmass production technology may be commercially implemented in the futurethat enables large quantities of single-layer disks to be trimmed with aprocessing accuracy of 0.1 μm at low cost. Even in that case, since thetop and bottom disks are trimmed simultaneously in the case of thetwo-layer laminated disk 800, the two disks must be laminated togetherwith the pit locations and optical marks aligned with an accuracy of afew microns. However, it is next to impossible to laminate the diskswith this accuracy because of the temperature coefficient, etc. of thepolycarbonate substrate. When optical marks were formed by applyinglaser light penetrating through the two-layer disk 800, the resultinganti-piracy mark is extremely difficult to duplicate. This provides agreater anti-piracy effect. The optical disk with an anti-piracymechanism is thus completed. For piracy prevention applications, incases where the disk process and laser cut process are inseparable as inthe case of the single-plate type, the encryption process, which is anintegral part of the laser cut process, and processing involving asecret encryption key have to be performed at the disk manufacturingfactory. This means that in the case of the single-plate type the secretencryption key maintained in the software company have to be deliveredto the disk manufacturing factory. This greatly reduces the security ofencryption. On the other hand, according to the method involving laserprocessing of laminated disks, which constitutes one aspect of theinvention, the laser trimming process can be completely separated fromthe disk manufacturing process. Therefore, laser trimming and encryptionoperations can be performed at a factory of the software maker. Sincethe secret encryption key that the software maker keeps need not bedelivered to the disk manufacturing factory, the secret key forencryption can be kept in the safe custody of the software maker. Thisgreatly increases the security of encryption.

(E) As described above, in the present invention, a legitimatemanufacturer can make a legitimate disk by processing the disk using ageneral-purpose laser trimming apparatus having a processing accuracy ofseveral tens of microns. Though a measuring accuracy of 0.13 μm isrequired, this can be achieved by conventional circuitry contained in aconsumer DVD player. By encrypting the measured result with a secretencryption key, a legitimate disk can be manufactured. That is, thelegitimate manufacturer need only have a secret key and a measuringapparatus with a measuring accuracy of 0.13 μm, while the requiredprocessing accuracy is two or three orders of magnitude lower, that is,several tens of microns. This means that a convectional laser processingapparatus can be used. On the other hand, an illegal manufacturer, whodoes not have a secret key, will have to directly copy the encryptedinformation recorded on the legitimate disk. This means that a physicalmark corresponding to the encrypted position information, that is, theposition information on the legitimate disk, must be formed with aprocessing accuracy of 0.13 μm. That is, the low reflective mark has tobe formed using a processing apparatus having a processing accuracy twoorders of magnitude higher than that of the processing apparatus used bythe legitimate manufacturer. Volume production with an accuracy higherby two orders of magnitude, i.e., with an accuracy of 0.1 μm, isdifficult both technically and economically, even in the foreseeablefuture. This means that production of pirated disks can be preventedduring the life of the DVD standard. One point of the invention is toexploit the fact that the measuring accuracy is generally a few ordersof magnitude higher than the processing accuracy.

In the case of CLV, the above method exploits the fact that the addresscoordinate arrangement differs from one master disk to another, aspreviously noted. FIG. 48 shows the result of the measurement of addresslocations on actual CDs. Generally, there are two types of master disk,one recorded by rotating a motor at a constant rotational speed, i.e.,with a constant angular velocity (CAV), and the other recorded byrotating a disk with a constant linear velocity (CLV). In the case of aCAV disk, since a logical address is located on a predetermined angularposition on the disk, the logical address and its physical angularposition on the disk are exactly the same no matter how many masterdisks are made. On the other hand, in the case of a CLV disk, since onlythe linear velocity is controlled, the angular position of the logicaladdress on the master disk is random. As can be seen from the result ofthe measurement of logical address locations on actual CDs in FIG. 48,the tracking pitch, start point and linear velocity vary slightly fromdisk to disk even if exactly the same data is recorded using the samemastering apparatus, and these errors accumulate, resulting in differentphysical locations. In FIG. 48, the locations of each logical address ona first master disk are indicated by white circles, and the locations onsecond and third master disks are indicated by black circles andtriangles, respectively. As can be seen, the physical locations of thelogical addresses vary each time the master disk is made. FIG. 17 showsthe low reflectivity portion address tables for a legitimate disk and anillegally duplicated disk for comparison.

The method of piracy prevention at the master disk level has beendescribed above. This is, when master disks of CLV recording, such as aCD or DVD, are made from the same logic data by using a masteringapparatus, as shown in FIG. 48, the physical location of each pit on thedisk varies between master disks, that is, between the legitimate diskand pirated disk This method distinguishes a pirated disk from alegitimate disk by taking advantage of this characteristic. The piracyprevention technology at the master disk level can prevent pirated disksat the logic level made by simply copying data only from the legitimatedisk. However, recent years have seen the emergence of piratemanufacturers equipped with more advanced technologies, who can make amaster disk replica identical in physical feature to a legitimate diskby melting the polycarbonate substrate of the legitimate disk. In thiscase, the piracy prevention method at the master disk level is defeated.To prevent this new threat of pirated disk production, the presentinvention has devised the piracy prevention method at the reflectivelayer level wherein a marking is formed on a reflective film.

According to the method of the present invention, the marking is formedon each disk pressed from a master disk, even if disks are pressed fromthe master disk, by removing a portion of the reflective film in thereflective film formation process. As a result, the position and shapeof the resulting low reflective marking is different from one disk toanother. In a usual process, it is next to impossible to partiallyremove the reflective film with an accuracy of submicrons. This servesto enhance the effectiveness in preventing duplication since duplicatingthe disk of the invention does not justify the cost.

FIG. 19 shows a flowchart for detecting a duplicated CD by using the lowreflectivity portion address table. The delay time needed to detect theoptical mark varies only slightly due to the optical head and circuitdesigns of the reproduction apparatus used. This of the delay time TDcircuit can be predicted at the design stage or at the time of massproduction. The optical mark position information is obtained bymeasuring the number of clocks, that is, the time, from the framesynchronizing signal. Due to the effect of the circuit delay time, anerror may be caused to detected data of the optical mark positioninformation. As a result, a legitimate disk may be erroneously judged asbeing a pirated disk, inconveniencing a legitimate user. A measure toreduce the effect of the circuit delay time TD will be described below.Further, a scratch made on a disk after purchase may cause aninterruption in the reproduced clock signal, causing an error of a fewclocks in the measurement of the optical mark position information. Toaddress this problem, a tolerance 866 and a pass count 867, shown inFIG. 20, are recorded on a disk, and while allowing a certain degree oftolerance on the measured value according to the actual situation at thetime of reproduction, the reproduction operation is permitted when thepass count 867 is reached; the margin allowed for an error due to asurface scratch on the disk can be controlled by the copyright ownerprior to the shipment of the disk. This will be described with referenceto FIG. 19.

In FIG. 19, the disk is reproduced in step 865a to recover the encryptedposition information from the barcode recording portion or pit recordingportion of the present invention. In step 865b, decryption or signatureverification is performed, and in step 865c, a list of optical markposition information is recovered. Next, if the delay time TD of areproduction circuit is stored in the circuit delay time storing section608a in the reproduction apparatus of FIG. 15, TD is read out in step865h and the process proceeds to step 865x. If TD is not stored in thereproduction apparatus, or if a measurement instruction is recorded onthe disk, the process proceeds to step 865d to enter a reference delaytime measurement routine. When address Ns-1 is detected, the startposition of the next address Ns is found. The frame synchronizing signaland the reproduced clock are counted, and in step 865f, the referenceoptical mark is detected. In step 865g, the circuit delay time TD ismeasured and stored. This operation is the same as the operation to bedescribed later with reference to FIG. 16(7). In step 865x, the opticalmark located inside address Nm is measured. In steps 865i, 865j, 865k,and 865m, the optical mark position information is detected with aresolution of one clock unit, as in steps 865d, 865y, 865f, and 865y.Next, in step 865n, a pirated disk detection routine is entered. First,the circuit delay time TD is corrected. In step 865p, the tolerance 866,i.e., tA, and pass count 867 recorded on the disk, as shown in FIG. 20,are read to check whether or not the position information measured instep 865g falls within the tolerance tA. If the result is OK in step865r, then in step 865s it is checked whether the checked mark count hasreached the pass count. If the result is OK, then in step 865u the diskis judged as being a legitimate disk and reproduction is permitted. Ifthe pass count is not reached yet, the process returns to step 865z. Ifthe result is NO in step 865r, then it is checked in step 865f whetherthe error detection count is smaller than NA, and only when the resultis OK, the process returns to step 865s. If it is not OK, then in step865v the disk is judged as being an illegal disk and the operation isstopped.

As described, since the circuit delay time TD of the reproductionapparatus is stored in the IC ROM, optical mark position information canbe obtained with increased accuracy. Furthermore, by setting thetolerance 866 and pass count for the software on each disk, the criteriafor pirated disk detection can be changed according to the actualcondition to allow for a scratch made on the disk after purchase. Thishas the effect of reducing the probability of a legitimate disk beingerroneously judged as an illegal disk.

As described in the above mode of embodiment, the piracy preventionmethod at the reflective layer level forms a physical mark in thepre-pit area of the reflective film on the disk, instead of thepreviously practiced physical marking at the master disk level. Pirateddisk production can thus be prevented even if the disk is duplicated atthe master disk level.

In the above mode of embodiment, a new optical-disk recording means wasused that performs secondary recording on a two-disk laminated opticaldisk by using a laser. In the first step, physical marks were randomlyformed, and in the second step, the physical marks were measured with ameasuring accuracy as high as 0.13 μm. In the third step, their positioninformation was encrypted and, using the secondary recording means, theencrypted information was recorded as a barcode on the optical disk withan accuracy of several tens of microns which was the usual processingaccuracy. In this way, optical mark position information was obtainedwith an accuracy of, for example, 0.1 μm, much higher than theprocessing accuracy of a conventional apparatus. Since such opticalmarks cannot be formed with the accuracy of 0.1 μm by using commerciallyavailable equipment, production of pirated disks can be prevented.

In the above mode of embodiment, the position information of theanti-piracy mark of the invention, which differs from one disk toanother, was used as a disk identifier. The position information and thedisk serial number, i.e., the disk ID, were combined together andencrypted with a digital signature; the thus encrypted information wasconverted into a barcode and written in overwriting fashion to theprescribed region of the pre-pit area, thus appending an unalterabledisk ID to each disk. Since each completed disk has a different ID, thepassword is also different. The password for one disk does not work onother disks. This enhances password security. Furthermore, using thesecondary recording technique of the invention, the password issecondary-recorded on the disk, permanently making the disk an operabledisk.

The first-half part (I) has dealt mainly with one application mode ofthe barcode in which the barcode is used for a pirated-disk preventionmethod. In this case, as shown in FIG. 2, the barcode (stripes)584c-584e are written over the prescribed region (stripe area) of thepre-pit area; therefore, the tracking is disturbed in that prescribedregion. If a marking 584 by laser light is formed in the prescribedregion where the barcode, 584c-584e, is recorded, as shown in FIG. 2, itbecomes difficult to accurately measure the address/clock position ofthe marking. To avoid this problem, if, as shown in FIG. 39, the marking941 is formed in a pit area 941a at a radius position different from theradius position of the stripe area 923a, the position of the marking 941can be measured stably with an accuracy of one clock, as shown in FIG.20(5). This has the effect of being able to identify pirated disks morestably.

In this case, by forming a pinhole marking destroying only a few tracks,as shown in FIG. 39, not only errors can be minimized but piracyprevention can be accomplished within the scope of the current standard.

Alternatively, the marking 941 may be recorded in the guard-band area999 shown in FIG. 30. Since the guard-band area 999 contains no data butaddress information, this has the effect of avoiding destroying alreadyrecorded data by recording the marking 941.

The optical disk of the invention has a structure such that a reflectivefilm is sandwiched directly or indirectly between two members resistantto laser light and a marking is formed by laser on the reflective film.The above mode of embodiment has dealt with examples in which thisstructure is used for secondary recording of a barcode, etc. and apiracy prevention technique, but it will be appreciated that such astructure may also be applied to other techniques. In the above mode ofembodiment, the optical disk of the invention has been described asbeing fabricated by laminating two substrates with an adhesive layerinterposed therebetween. However, the adhesive layer may be omitted, orinstead, a member made of a different material, such as a protectivelayer, may be used; that is, any suitable structure may be used as longas the reflective film is sandwiched directly or indirectly between twomembers resistant to laser light. Furthermore, in the above mode ofembodiment, the optical disk of the invention has been described ascomprising substrates as the members that are laminated together, butother members such as protective layers may be used; that is, any memberthat has resistance to laser light may be used.

As described, according to the present invention, since an ID unique toeach individual disk, for example, is converted into a barcode andwritten in overwriting fashion to an ordinary pit area, both the pitdata and barcode data can be read by using the same optical pickup. Thishas the effect of simplifying the construction of the playbackapparatus, for example.

Furthermore, by barcoding the marking position information for use as adisk-unique ID, the invention provides a greatly improved pirated-diskand other illegal duplication prevention capability as compared to theprior art. A piracy prevention technique of the prior art, for example,employed a method that deliberately arranged pits in serpentine fashionwhen making a disk mold. Such a prior art method is not effective inpiracy prevention, since a pirated disk can be easily made by exactlyreplicating the mold shape from a legitimate optical disk. On the otherhand, according to the present invention, since the marking is formed onthe reflective film by a laser and its position information is coded asa barcode, as described above, the contents of them cannot be made tocoincide when making an illegal duplication. The above-described piracyprevention effect is thus accomplished.

What is claimed is:
 1. A reproducing apparatus for reproducinginformation on an optical disk where a first signal is recorded by a bitpattern with a first recording clock T1 and a second signal is recordedwith overlapping state on said first signal with a second recordingclock T2 (≧14T1), comprising high frequency suppressing means forsuppressing a high frequency signal which is higher than a predeterminedfrequency, and whereinsaid second signal is extracted from a reproducedinformation by suppressing said first signal by using said highfrequency suppressing means.
 2. A reproducing apparatus according toclaim 1, whereinsaid high frequency suppressing means is a low passfilter.
 3. An optical disk reproducing apparatus wherein recordedcontents of a recording area on which a main information recorded byforming pits on an optical disk are reproduced by an optical head withusing rotational phase control for a motor, while recorded contents of adifferent recording area other than said recording area, on which subinformation is recorded by selectively forming low-reflectivity marksare reproduced by an optical head using rotational speed control forsaid motor and therebythe main information recorded on said recordingarea and the sub information recorded on said different recording areaare both reproduced by using the same optical pickup.
 4. An optical diskreproducing apparatus according to claim 3, wherein tracking control isnot performed in said different recording area.
 5. An optical diskreproducing apparatus according to claim 3 wherein tracking control isperformed in said recording area.
 6. An optical disk reproducingapparatus according to claim 5, wherein said rotational speed is therotational speed that would be achieved in said different recording areaif said rotational phase control were applied.
 7. An optical diskreproducing apparatus according to claim 3, wherein the rotational speedof said motor in said rotational speed control is maintained at aprescribed value based on a result obtained by measuring aminimum-length pit in said different recording area.
 8. An optical diskreproducing apparatus according to claim 3, wherein said marks are abarcode-like pattern formed on a circle of a predetermined radius.
 9. Anoptical disk reproducing apparatus according to claim 3, whereinsaidmarks are a barcode-like pattern, and said different recording area isrecorded with pits, and when reproducing the recorded contents of saiddifferent recording area, a high-frequency-component signal generatedduring reproduction of said pits on said different recording area isreduced or eliminated by a low-pass filter thereby making it possible toseparate a signal which is reproduced from said barcode.
 10. An opticaldisk reproducing apparatus according to claim 3, whereinsaid marks are abarcode-like pattern and when reproducing the recorded contents of saiddifferent recording area, the width of a signal obtained by reading saidbarcode is increased to a prescribed width and then measured withsampling pulses from a control section.
 11. An optical disk reproducingapparatus according to any one of claims 3 to 10, wherein said opticaldisk is constructed from two disk-substrates laminated together.
 12. Anoptical disk reproducing apparatus according to claim 3, wherein saidoptical disk includes a control data area for holding therein physicalfeature information concerning said optical disk, and an identifier forindicating the presence or absence of said barcode is recorded in saidcontrol data area.
 13. An optical disk reproducing apparatus accordingto claim 12, wherein, after reading recorded contents of said controldata area and judging the presence or absence of said barcode, it isdetermined whether an optical pickup should be moved to an inner portionor an outer portion of said optical disk.